(window.webpackJsonp=window.webpackJsonp||[]).push([[2437],{2845:function(t,s,a){"use strict";a.r(s);var n=a(31),e=Object(n.a)({},(function(){var t=this,s=t.$createElement,a=t._self._c||s;return a("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[a("h1",{attrs:{id:"constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#constants"}},[t._v("#")]),t._v(" Constants")]),t._v(" "),a("h2",{attrs:{id:"defining-constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#defining-constants"}},[t._v("#")]),t._v(" Defining constants")]),t._v(" "),a("p",[t._v("Constants are created using the "),a("code",[t._v("const")]),t._v(" statement or the "),a("code",[t._v("define")]),t._v(" function. The convention is to use UPPERCASE letters for constant names.")]),t._v(" "),a("h3",{attrs:{id:"define-constant-using-explicit-values"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#define-constant-using-explicit-values"}},[t._v("#")]),t._v(" Define constant using explicit values")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("PI")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("3.14")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// float")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"EARTH_IS_FLAT"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("false")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// boolean")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"UNKNOWN"')]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("null")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// null")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"APP_ENV"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"dev"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// string")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("MAX_SESSION_TIME")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("60")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("*")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("60")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// integer, using (scalar) expressions is ok")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("APP_LANGUAGES")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"de"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"en"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// arrays")]),t._v("\n\n\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"BETTER_APP_LANGUAGES"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"lu"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"de"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// arrays")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"define-constant-using-another-constant"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#define-constant-using-another-constant"}},[t._v("#")]),t._v(" Define constant using another constant")]),t._v(" "),a("p",[t._v("if you have one constant you can define another one based on it:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("TAU")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("PI")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("*")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"EARTH_IS_ROUND"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("EARTH_IS_FLAT")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"MORE_UNKNOWN"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("UNKNOWN")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"APP_ENV_UPPERCASE"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("strtoupper")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("APP_ENV")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// string manipulation is ok too")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// the above example (a function call) does not work with const:")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// const TIME = time(); # fails with a fatal error! Not a constant scalar expression")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"MAX_SESSION_TIME_IN_MINUTES"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("MAX_SESSION_TIME")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("/")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("60")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("APP_FUTURE_LANGUAGES")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("-")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=>")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"es"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("APP_LANGUAGES")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// array manipulations")]),t._v("\n\n\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"APP_BETTER_FUTURE_LANGUAGES"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("array_merge")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"fr"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("APP_BETTER_LANGUAGES")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"reserved-constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#reserved-constants"}},[t._v("#")]),t._v(" Reserved constants")]),t._v(" "),a("p",[t._v("Some constant names are reserved by PHP and cannot be redefined. All these examples will fail:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"true"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("false")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// internal constant")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"false"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("true")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// internal constant")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"CURLOPT_AUTOREFERER"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"something"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// will fail if curl extension is loaded")]),t._v("\n\n")])])]),a("p",[t._v("And a Notice will be issued:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[t._v("Constant "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("...")]),t._v(" already defined in "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("...")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"conditional-defines"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#conditional-defines"}},[t._v("#")]),t._v(" Conditional defines")]),t._v(" "),a("p",[t._v("If you have several files where you may define the same variable (for example, your main config then your local config) then following syntax may help avoiding conflicts:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token function"}},[t._v("defined")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"PI"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("||")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"PI"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("3.1415")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// "define PI if it\'s not yet defined"')]),t._v("\n\n")])])]),a("h3",{attrs:{id:"const-vs-define"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#const-vs-define"}},[t._v("#")]),t._v(" "),a("code",[t._v("const")]),t._v(" vs "),a("code",[t._v("define")])]),t._v(" "),a("p",[a("code",[t._v("define")]),t._v(" is a runtime expression while "),a("code",[t._v("const")]),t._v(" a compile time one.")]),t._v(" "),a("p",[t._v("Thus "),a("code",[t._v("define")]),t._v(" allows for dynamic values (i.e. function calls, variables etc.) and even dynamic names and conditional definition. It however is always defining relative to the root namespace.")]),t._v(" "),a("p",[a("code",[t._v("const")]),t._v(" is static (as in allows only operations with other constants, scalars or arrays, and only a restricted set of them, the so called "),a("strong",[t._v("constant scalar expressions")]),t._v(", i.e. arithmetic, logical and comparison operators as well as array dereferencing), but are automatically namespace prefixed with the currently active namespace.")]),t._v(" "),a("p",[a("code",[t._v("const")]),t._v(" only supports other constants and scalars as values, and no operations.")]),t._v(" "),a("h2",{attrs:{id:"class-constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#class-constants"}},[t._v("#")]),t._v(" Class Constants")]),t._v(" "),a("p",[t._v("Constants can be defined inside classes using a "),a("code",[t._v("const")]),t._v(" keyword.")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("class")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name-definition class-name"}},[t._v("Foo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("BAR_TYPE")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"bar"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// reference from inside the class using self::")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function-definition function"}},[t._v("myMethod")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword static-context"}},[t._v("self")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("BAR_TYPE")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// reference from outside the class using <ClassName>::")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("Foo")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("BAR_TYPE")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("This is useful to store types of items.")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token php language-php"}},[a("span",{pre:!0,attrs:{class:"token delimiter important"}},[t._v("<?php")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("class")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name-definition class-name"}},[t._v("Logger")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("LEVEL_INFO")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("LEVEL_WARNING")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("LEVEL_ERROR")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// we can even assign the constant as a default value")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function-definition function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$message")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$level")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword static-context"}},[t._v("self")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("LEVEL_INFO")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"Message level "')]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(".")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$level")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(".")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('": "')]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(".")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$message")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$logger")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Logger")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$logger")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"Info"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Using default value")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$logger")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"Warning"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$logger")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("LEVEL_WARNING")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Using var")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$logger")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"Error"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("Logger")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("LEVEL_ERROR")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// using class")]),t._v("\n\n")])])])]),a("h2",{attrs:{id:"checking-if-constant-is-defined"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#checking-if-constant-is-defined"}},[t._v("#")]),t._v(" Checking if constant is defined")]),t._v(" "),a("h3",{attrs:{id:"simple-check"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#simple-check"}},[t._v("#")]),t._v(" Simple check")]),t._v(" "),a("p",[t._v("To check if constant is defined use the "),a("code",[t._v("defined")]),t._v(" function. Note that this function doesn't care about constant's value, it only cares if the constant exists or not. Even if the value of the constant is "),a("code",[t._v("null")]),t._v(" or "),a("code",[t._v("false")]),t._v(" the function will still return "),a("code",[t._v("true")]),t._v(".")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token php language-php"}},[a("span",{pre:!0,attrs:{class:"token delimiter important"}},[t._v("<?php")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("false")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("defined")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD is defined"')]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// prints "GOOD is defined"')]),t._v("\n\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("GOOD")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD is true"')]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// does not print anything, since GOOD is false")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("defined")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"AWESOME"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n   "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"AWESOME"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("true")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// awesome was not defined. Now we have defined it ")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])])]),a("p",[t._v('Note that constant becomes "visible" in your code only '),a("strong",[t._v("after")]),t._v(" the line where you have defined it:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token php language-php"}},[a("span",{pre:!0,attrs:{class:"token delimiter important"}},[t._v("<?php")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("defined")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n   "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD is defined"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// doesn't print anyhting, GOOD is not defined yet.")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("false")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("defined")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n   "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"GOOD is defined"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// prints "GOOD is defined"')]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])])]),a("h3",{attrs:{id:"getting-all-defined-constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#getting-all-defined-constants"}},[t._v("#")]),t._v(" Getting all defined constants")]),t._v(" "),a("p",[t._v("To get all defined constants including those created by PHP use the "),a("code",[t._v("get_defined_constants")]),t._v(" function:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token php language-php"}},[a("span",{pre:!0,attrs:{class:"token delimiter important"}},[t._v("<?php")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$constants")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("get_defined_constants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("var_dump")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$constants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// pretty large list")]),t._v("\n\n")])])])]),a("p",[t._v("To get only those constants that were defined by your app call the function at the beginning and at the end of your script (normally after the bootstrap process):")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token php language-php"}},[a("span",{pre:!0,attrs:{class:"token delimiter important"}},[t._v("<?php")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$constants")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("get_defined_constants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"HELLO"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"hello"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"WORLD"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"world"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$new_constants")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("get_defined_constants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$myconstants")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("array_diff_assoc")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$new_constants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$constants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("var_export")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$myconstants")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n   \n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("/* \nOutput:\n\narray (\n  'HELLO' => 'hello',\n  'WORLD' => 'world',\n) \n*/")]),t._v("\n\n")])])])]),a("p",[t._v("It's sometimes useful for debugging")]),t._v(" "),a("h2",{attrs:{id:"constant-arrays"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#constant-arrays"}},[t._v("#")]),t._v(" Constant arrays")]),t._v(" "),a("p",[t._v("Arrays can be used as plain constants and class constants from version PHP 5.6 onwards:")]),t._v(" "),a("h3",{attrs:{id:"class-constant-example"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#class-constant-example"}},[t._v("#")]),t._v(" Class constant example")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("class")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name-definition class-name"}},[t._v("Answer")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("C")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("Answer")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("C")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(".")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("Answer")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("C")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 42")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"plain-constant-example"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#plain-constant-example"}},[t._v("#")]),t._v(" Plain constant example")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("ANSWER")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("ANSWER")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(".")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("ANSWER")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 42")]),t._v("\n\n")])])]),a("p",[t._v("Also from version PHP 7.0 this functionality was ported to the "),a("a",{attrs:{href:"http://php.net/manual/en/function.define.php",target:"_blank",rel:"noopener noreferrer"}},[a("code",[t._v("define")]),a("OutboundLink")],1),t._v(" function for plain constants.")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'VALUES'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("define")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'MY_ARRAY'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("VALUES")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("MY_ARRAY")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 3")]),t._v("\n\n")])])]),a("h2",{attrs:{id:"using-constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#using-constants"}},[t._v("#")]),t._v(" Using constants")]),t._v(" "),a("p",[t._v("To use the constant simply use its name:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("EARTH_IS_FLAT")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"Earth is flat"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("APP_ENV_UPPERCASE")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("or if you don't know the name of the constant in advance, use the "),a("code",[t._v("constant")]),t._v(" function:")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// this code is equivalent to the above code")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$const1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"EARTH_IS_FLAT"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$const2")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"APP_ENV_UPPERCASE"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("constant")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$const1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"Earth is flat"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("print")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("constant")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$const2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("h4",{attrs:{id:"syntax"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#syntax"}},[t._v("#")]),t._v(" Syntax")]),t._v(" "),a("ul",[a("li",[t._v("define ( string $name , mixed $value [, bool $case_insensitive = false ] )")]),t._v(" "),a("li",[t._v("const CONSTANT_NAME = VALUE;")])]),t._v(" "),a("h4",{attrs:{id:"remarks"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#remarks"}},[t._v("#")]),t._v(" Remarks")]),t._v(" "),a("p",[a("a",{attrs:{href:"http://php.net/manual/en/language.constants.php",target:"_blank",rel:"noopener noreferrer"}},[t._v("Constants"),a("OutboundLink")],1),t._v(" are used to store the values that are not supposed to be changed later. They also are often used to store the configuration parameters especially those which define the environment (dev/production).")]),t._v(" "),a("p",[t._v("Constants have types like variables but not all types can be used to initialize a constant. Objects and resources cannot be used as values for constants at all. Arrays can be used as constants starting from PHP 5.6")]),t._v(" "),a("p",[t._v("Some constant names are reserved by PHP. These include "),a("code",[t._v("true")]),t._v(", "),a("code",[t._v("false")]),t._v(", "),a("code",[t._v("null")]),t._v(" as well as many module-specific constants.")]),t._v(" "),a("p",[t._v("Constants are usually named using uppercase letters.")])])}),[],!1,null,null,null);s.default=e.exports}}]);