(window.webpackJsonp=window.webpackJsonp||[]).push([[2484],{2893:function(t,s,a){"use strict";a.r(s);var e=a(31),n=Object(e.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:"operators"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#operators"}},[t._v("#")]),t._v(" Operators")]),t._v(" "),a("p",[t._v("An operator is something that takes one or more values (or expressions, in programming jargon) and yields another value (so that the construction itself becomes an expression).")]),t._v(" "),a("p",[t._v("Operators can be grouped according to the number of values they take.")]),t._v(" "),a("h2",{attrs:{id:"null-coalescing-operator"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#null-coalescing-operator"}},[t._v("#")]),t._v(" Null Coalescing Operator (??)")]),t._v(" "),a("p",[t._v("Null coalescing is a new operator introduced in PHP 7. This operator returns its first operand if it is set and not "),a("code",[t._v("NULL")]),t._v(". 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It consists of three parts. The "),a("code",[t._v("operator")]),t._v(", and two outcomes. The syntax is as follows:")]),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 variable"}},[t._v("$value")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<")]),t._v("operator"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(">")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("?")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<")]),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("true")]),t._v(" value"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(">")]),t._v(" "),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 boolean"}},[t._v("false")]),t._v(" value"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(">")]),t._v("\n\n")])])]),a("p",[t._v("If the "),a("code",[t._v("operator")]),t._v(" is evaluated as "),a("code",[t._v("true")]),t._v(", the value in the first block will be returned ("),a("code",[t._v("<true value>")]),t._v("), else the value in the second block will be returned ("),a("code",[t._v("<false value>")]),t._v("). 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"),a("code",[t._v("?:")]),t._v(" is often referred to as "),a("strong",[t._v("Elvis")]),t._v(" operator.")]),t._v(" "),a("p",[t._v("This behaves like the "),a("a",{attrs:{href:"http://stackoverflow.com/documentation/php/1687/operators/7164/null-coalescing-operator",target:"_blank",rel:"noopener noreferrer"}},[t._v("Null Coalescing operator "),a("code",[t._v("??")]),a("OutboundLink")],1),t._v(", except that "),a("code",[t._v("??")]),t._v(" requires the left operand to be exactly "),a("code",[t._v("null")]),t._v(" while "),a("code",[t._v("?:")]),t._v(" tries to resolve the left operand into a boolean and check if it resolves to boolean "),a("code",[t._v("false")]),t._v(".")]),t._v(" "),a("p",[t._v("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("function")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function-definition function"}},[t._v("setWidth")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token keyword type-hint"}},[t._v("int")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$width")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),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("\n    "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$_SESSION")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"width"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$width")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("?")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("getDefaultWidth")]),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 punctuation"}},[t._v("}")]),t._v("\n\n")])])]),a("p",[t._v("In this example, "),a("code",[t._v("setWidth")]),t._v(" accepts a width parameter, or default 0, to change the width session value. If "),a("code",[t._v("$width")]),t._v(" is 0 (if "),a("code",[t._v("$width")]),t._v(" is not provided), which will resolve to boolean false, the value of "),a("code",[t._v("getDefaultWidth()")]),t._v(" is used instead. The "),a("code",[t._v("getDefaultWidth()")]),t._v(" function will not be called if "),a("code",[t._v("$width")]),t._v(" did not resolve to boolean false.")]),t._v(" "),a("p",[t._v("Refer to "),a("a",{attrs:{href:"http://stackoverflow.com/documentation/php/232/php-types",target:"_blank",rel:"noopener noreferrer"}},[t._v("Types"),a("OutboundLink")],1),t._v(" for more information about conversion of variables to boolean.")]),t._v(" "),a("h2",{attrs:{id:"incrementing-and-decrementing-operators"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#incrementing-and-decrementing-operators"}},[t._v("#")]),t._v(" Incrementing (++) and Decrementing Operators (--)")]),t._v(" "),a("p",[t._v("Variables can be incremented or decremented by 1 with "),a("code",[t._v("++")]),t._v(" or "),a("code",[t._v("--")]),t._v(", respectively. They can either precede or succeed variables and slightly vary semantically, as shown below.")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$i")]),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("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$i")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Prints 1")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Pre-increment operator increments $i by one, then returns $i")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("++")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$i")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Prints 2")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Pre-decrement operator decrements $i by one, then returns $i")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("--")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$i")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Prints 1")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Post-increment operator returns $i, then increments $i by one")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$i")]),a("span",{pre:!0,attrs:{class:"token operator"}},[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 1 (but $i value is now 2)")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Post-decrement operator returns $i, then decrements $i by one")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$i")]),a("span",{pre:!0,attrs:{class:"token operator"}},[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 2 (but $i value is now 1)")]),t._v("\n\n")])])]),a("p",[t._v("More information about incrementing and decrementing operators can be found in the "),a("a",{attrs:{href:"http://php.net/manual/en/language.operators.increment.php",target:"_blank",rel:"noopener noreferrer"}},[t._v("official documentation"),a("OutboundLink")],1),t._v(".")]),t._v(" "),a("h2",{attrs:{id:"execution-operator"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#execution-operator"}},[t._v("#")]),t._v(" Execution Operator (``)")]),t._v(" "),a("p",[t._v("The PHP execution operator consists of backticks (``) and is used to run shell commands. The output of the command will be returned, and may, therefore, be stored in a variable.")]),t._v(" "),a("div",{staticClass:"language-php extra-class"},[a("pre",{pre:!0,attrs:{class:"language-php"}},[a("code",[a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// List files")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$output")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string backtick-quoted-string"}},[t._v("`ls`")]),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('"<pre>'),a("span",{pre:!0,attrs:{class:"token interpolation"}},[a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$output")])]),t._v('</pre>"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("Note that the execute operator and "),a("a",{attrs:{href:"http://php.net/manual/en/function.shell-exec.php",target:"_blank",rel:"noopener noreferrer"}},[a("code",[t._v("shell_exec()")]),a("OutboundLink")],1),t._v(" will give the same result.")]),t._v(" "),a("h2",{attrs:{id:"logical-operators-and-and-or"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#logical-operators-and-and-or"}},[t._v("#")]),t._v(" Logical Operators (&&/AND and ||/OR)")]),t._v(" "),a("p",[t._v("In PHP, there are two versions of logical AND and OR operators.")]),t._v(" "),a("table",[a("thead",[a("tr",[a("th",[t._v("Operator")]),t._v(" "),a("th",[t._v("True if")])])]),t._v(" "),a("tbody",[a("tr",[a("td",[a("code",[t._v("$a and $b")])]),t._v(" "),a("td",[t._v("Both "),a("code",[t._v("$a")]),t._v(" and "),a("code",[t._v("$b")]),t._v(" are true")])]),t._v(" "),a("tr",[a("td",[a("code",[t._v("$a && $b")])]),t._v(" "),a("td",[t._v("Both "),a("code",[t._v("$a")]),t._v(" and "),a("code",[t._v("$b")]),t._v(" are true")])]),t._v(" "),a("tr",[a("td",[a("code",[t._v("$a or $b")])]),t._v(" "),a("td",[t._v("Either "),a("code",[t._v("$a")]),t._v(" or "),a("code",[t._v("$b")]),t._v(" is true")])]),t._v(" "),a("tr",[a("td",[a("code",[t._v("$a || $b")])]),t._v(" "),a("td",[t._v("Either "),a("code",[t._v("$a")]),t._v(" or "),a("code",[t._v("$b")]),t._v(" is true")])])])]),t._v(" "),a("p",[t._v("Note that the "),a("code",[t._v("&&")]),t._v(" and "),a("code",[t._v("||")]),t._v(" opererators have higher "),a("a",{attrs:{href:"http://php.net/manual/en/language.operators.precedence.php",target:"_blank",rel:"noopener noreferrer"}},[t._v("precedence"),a("OutboundLink")],1),t._v(" than "),a("code",[t._v("and")]),t._v(" and "),a("code",[t._v("or")]),t._v(". See table below:")]),t._v(" "),a("table",[a("thead",[a("tr",[a("th",[t._v("Evaluation")]),t._v(" "),a("th",[t._v("Result of "),a("code",[t._v("$e")])]),t._v(" "),a("th",[t._v("Evaluated as")])])]),t._v(" "),a("tbody",[a("tr",[a("td",[a("code",[t._v("$e = false || true")])]),t._v(" "),a("td",[t._v("True")]),t._v(" "),a("td",[a("code",[t._v("$e = (false || true)")])])]),t._v(" "),a("tr",[a("td",[a("code",[t._v("$e = false or true")])]),t._v(" "),a("td",[t._v("False")]),t._v(" "),a("td",[a("code",[t._v("($e = false) or true")])])])])]),t._v(" "),a("p",[t._v("Because of this it's safer to use "),a("code",[t._v("&&")]),t._v(" and "),a("code",[t._v("||")]),t._v(" instead of "),a("code",[t._v("and")]),t._v(" and "),a("code",[t._v("or")]),t._v(".")]),t._v(" "),a("h2",{attrs:{id:"string-operators-and"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#string-operators-and"}},[t._v("#")]),t._v(" String Operators (. and .=)")]),t._v(" "),a("p",[t._v("There are only two string 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function"}},[t._v("var_dump")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("8")]),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("// prints bool(true)")]),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 number"}},[t._v("9")]),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(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// prints bool(false)")]),t._v("\n\n")])])]),a("p",[t._v("5/6. "),a("strong",[t._v("Not Equal/Identical To:")]),t._v(" To rehash the earlier example on equality, the sample below will display 'a and b are not identical', but not 'a and b are not equal'.")]),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 variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$b")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'4'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\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 variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$b")]),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 single-quoted-string"}},[t._v("'a and b are not equal'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// this won't be printed")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\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 variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!==")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$b")]),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 single-quoted-string"}},[t._v("'a and b are not identical'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// this will be printed")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),a("h2",{attrs:{id:"instanceof-type-operator"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#instanceof-type-operator"}},[t._v("#")]),t._v(" instanceof (type operator)")]),t._v(" "),a("p",[t._v("For checking whether some object is of a certain class, the (binary) "),a("code",[t._v("instanceof")]),t._v(" operator can be used since PHP version 5.")]),t._v(" "),a("p",[t._v("The first (left) parameter is the object to test. If this variable is not an object, "),a("code",[t._v("instanceof")]),t._v(" always returns "),a("code",[t._v("false")]),t._v(". If a constant expression is used, an error is thrown.")]),t._v(" "),a("p",[t._v("The second (right) parameter is the class to compare with. The class can be provided as the class name itself, a string variable containing the class name (not a string constant!) or an object of that class.")]),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("MyClass")]),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 variable"}},[t._v("$o1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("MyClass")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$o2")]),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("MyClass")]),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("$name")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'MyClass'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// in the cases below, $a gets boolean value true")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$o1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("instanceof")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("MyClass")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$o1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("instanceof")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$name")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$o1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("instanceof")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$o2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// counter examples:")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$b")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'b'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$o1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("instanceof")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'MyClass'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// parse error: constant not allowed")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant boolean"}},[t._v("false")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("instanceof")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("MyClass")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// fatal error: constant not allowed")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$b")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("instanceof")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("MyClass")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// false ($b is not an object)")]),t._v("\n\n")])])]),a("p",[a("code",[t._v("instanceof")]),t._v(" can also be used to check whether an object is of some class which extends another class or implements some interface:")]),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("interface")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name-definition class-name"}},[t._v("MyInterface")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token 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"),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("OtherClass")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// true")]),t._v("\n\n")])])]),a("p",[t._v("Note that parentheses around "),a("code",[t._v("$o instanceof MyClass")]),t._v(" are not needed because "),a("code",[t._v("instanceof")]),t._v(" has higher precedence than "),a("code",[t._v("!")]),t._v(", although it may make the code better readable "),a("strong",[t._v("with")]),t._v(" parentheses.")]),t._v(" "),a("h3",{attrs:{id:"caveats"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#caveats"}},[t._v("#")]),t._v(" Caveats")]),t._v(" "),a("p",[t._v("If a class does not exist, the registered autoload functions are called to try to define the class (this is a topic outside the scope of this part of the Documentation!). In PHP versions before 5.1.0, the "),a("code",[t._v("instanceof")]),t._v(" operator would also trigger these calls, thus actually defining the class (and if the class could not be defined, a fatal error would occur). 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This function was deprecated in PHP version 5 and undeprecated in PHP version 5.3.0.")]),t._v(" "),a("h2",{attrs:{id:"bitwise-operators"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#bitwise-operators"}},[t._v("#")]),t._v(" Bitwise Operators")]),t._v(" "),a("h3",{attrs:{id:"prefix-bitwise-operators"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#prefix-bitwise-operators"}},[t._v("#")]),t._v(" Prefix bitwise operators")]),t._v(" "),a("p",[t._v("Bitwise operators are like logical operators but executed per bit rather than per boolean value.")]),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("// bitwise NOT ~: sets all unset bits and unsets all set bits")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("printf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"%\'06b"')]),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 number"}},[t._v("0b110110")]),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("// 001001")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"bitmask-bitmask-operators"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#bitmask-bitmask-operators"}},[t._v("#")]),t._v(" Bitmask-bitmask operators")]),t._v(" "),a("p",[t._v("Bitwise AND "),a("code",[t._v("&")]),t._v(": a bit is set only if it is set in both operands")]),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("printf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"%\'06b"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0b110101")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0b011001")]),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("// 010001")]),t._v("\n\n")])])]),a("p",[t._v("Bitwise OR "),a("code",[t._v("|")]),t._v(":  a bit is set if it is set in either or both operands")]),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("printf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"%\'06b"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0b110101")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("|")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0b011001")]),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("// 111101")]),t._v("\n\n")])])]),a("p",[t._v("Bitwise XOR "),a("code",[t._v("^")]),t._v(": a bit is set if it is set in one operand and not set in another operand, i.e. only if that bit is in different state in the two operands")]),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("printf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"%\'06b"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0b110101")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("^")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0b011001")]),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("// 101100")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"example-uses-of-bitmasks"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#example-uses-of-bitmasks"}},[t._v("#")]),t._v(" Example uses of bitmasks")]),t._v(" "),a("p",[t._v("These operators can be used to manipulate bitmasks. For 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 function"}},[t._v("file_put_contents")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"file.log"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LOCK_EX")]),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("FILE_APPEND")]),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("p",[t._v("Here, the "),a("code",[t._v("|")]),t._v(" operator is used to combine the two bitmasks. Although "),a("code",[t._v("+")]),t._v(" has the same effect, "),a("code",[t._v("|")]),t._v(" emphasizes that you are combining bitmasks, not adding two normal scalar integers.")]),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")]),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("OPTION_A")]),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(" 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0")]),t._v(")")])]),t._v(" "),a("li",[a("p",[t._v("If the output has any bits set, it means that any one of the options are enabled.")])]),t._v(" "),a("li",[a("p",[t._v("If the output has all bits of the bitmask set, it means that all of the options in the bitmask are enabled.")])])]),t._v(" "),a("p",[t._v("Bear in mind that these comparison operators: ("),a("code",[t._v("<")]),t._v(" "),a("code",[t._v(">")]),t._v(" "),a("code",[t._v("<=")]),t._v(" "),a("code",[t._v(">=")]),t._v(" "),a("code",[t._v("==")]),t._v(" "),a("code",[t._v("===")]),t._v(" "),a("code",[t._v("!=")]),t._v(" "),a("code",[t._v("!==")]),t._v(" "),a("code",[t._v("<>")]),t._v(" "),a("code",[t._v("<=>")]),t._v(") have higher precedence than these bitmask-bitmask operators: ("),a("code",[t._v("|")]),t._v(" "),a("code",[t._v("^")]),t._v(" "),a("code",[t._v("&")]),t._v("). As bitwise results are often compared using these comparison operators, this is a common pitfall to be aware of.")]),t._v(" "),a("h3",{attrs:{id:"bit-shifting-operators"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#bit-shifting-operators"}},[t._v("#")]),t._v(" Bit-shifting operators")]),t._v(" "),a("p",[t._v("Bitwise left shift "),a("code",[t._v("<<")]),t._v(": shift all bits to the left (more significant) by the given number of steps and discard the bits exceeding the int size")]),t._v(" "),a("p",[a("code",[t._v("<< $x")]),t._v(" is equivalent to unsetting the highest "),a("code",[t._v("$x")]),t._v(" bits and multiplying by the "),a("code",[t._v("$x")]),t._v("th power of 2")]),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("printf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string 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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("// 7FFFFFFC, FFFFFFFF")]),t._v("\n\n")])])]),a("p",[t._v("Bitwise right shift "),a("code",[t._v(">>")]),t._v(": discard the lowest shift and shift the remaining bits to the right (less significant)")]),t._v(" "),a("p",[a("code",[t._v(">> $x")]),t._v(" is equivalent to dividing by the "),a("code",[t._v("$x")]),t._v("th power of 2 and discard the non-integer part")]),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("printf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"%x"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token 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It outputs the value in 6 binary digits.")]),t._v(" "),a("h4",{attrs:{id:"remarks"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#remarks"}},[t._v("#")]),t._v(" Remarks")]),t._v(" "),a("p",[t._v("Operators 'operate' or act on one (unary operators such as "),a("code",[t._v("!$a")]),t._v(" and "),a("code",[t._v("++$a")]),t._v("), two (binary operators such as "),a("code",[t._v("$a + $b")]),t._v(" or "),a("code",[t._v("$a >> $b")]),t._v(") or three (the only ternary operator is "),a("code",[t._v("$a ? $b : $c")]),t._v(") expressions.")]),t._v(" "),a("p",[t._v("Operator precedence influences how operators are grouped (as if there were parentheses). The following is a list of operators in order of there precendence (operators in the second column). 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Special care is needed if the parentheses after a language construct are omitted. E.g. "),a("code",[t._v("echo 2 . print 3 + 4;")]),t._v(" echo's "),a("code",[t._v("721")]),t._v(": the "),a("code",[t._v("print")]),t._v(" part evaluates "),a("code",[t._v("3 + 4")]),t._v(", prints the outcome "),a("code",[t._v("7")]),t._v(" and returns "),a("code",[t._v("1")]),t._v(". After that, "),a("code",[t._v("2")]),t._v(" is echoed, concatenated with the return value of "),a("code",[t._v("print")]),t._v(" ("),a("code",[t._v("1")]),t._v(").")])])}),[],!1,null,null,null);s.default=n.exports}}]);