(window.webpackJsonp=window.webpackJsonp||[]).push([[2428],{2838: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:"classes-and-objects"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#classes-and-objects"}},[t._v("#")]),t._v(" Classes and Objects")]),t._v(" "),a("p",[t._v("Classes and Objects are used to to make your code more efficient and less repetitive by grouping similar tasks.")]),t._v(" "),a("p",[t._v("A class is used to define the actions and data structure used to build objects. The objects are then built using this predefined structure.")]),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("Class constants provide a mechanism for holding fixed values in a program. 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It also ensures that misspellings cannot make it past the compiler. While "),a("code",[t._v("new Pie('aple')")]),t._v(" and "),a("code",[t._v("new Pie('apple')")]),t._v(" are both acceptable to the compiler, "),a("code",[t._v("new Pie(Fruit::APLE)")]),t._v(" will produce a compiler error.")]),t._v(" "),a("p",[t._v("Finally, using class constants means that the actual value of the constant may be modified in a single place, and any code using the constant automatically has the effects of the modification.")]),t._v(" "),a("p",[t._v("Whilst the most common method to access a class constant is "),a("code",[t._v("MyClass::CONSTANT_NAME")]),t._v(", it may also be accessed by:")]),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("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("MyClass")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("CONSTANT")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$classname")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('"MyClass"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$classname")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("CONSTANT")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// As of PHP 5.3.0")]),t._v("\n\n")])])]),a("p",[t._v("Class constants in PHP are conventionally named all in uppercase with underscores as word separators, although any valid label name may be used as a class constant name.")]),t._v(" "),a("p",[t._v("As of PHP 7.1, class constants may now be defined with different visibilities from the default public scope. This means that both protected and private constants can now be defined to prevent class constants from unnecessarily leaking into the public scope (see "),a("a",{attrs:{href:"http://stackoverflow.com/documentation/php/504/classes-and-objects/6471/method-and-property-visibility",target:"_blank",rel:"noopener noreferrer"}},[t._v("Method and Property Visibility"),a("OutboundLink")],1),t._v(" ). 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 keyword"}},[t._v("class")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name-definition class-name"}},[t._v("Something")]),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("PUBLIC_CONST_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("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("PUBLIC_CONST_B")]),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("protected")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("PROTECTED_CONST")]),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    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("private")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("PRIVATE_CONST")]),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 punctuation"}},[t._v("}")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"define-vs-class-constants"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#define-vs-class-constants"}},[t._v("#")]),t._v(" define vs class constants")]),t._v(" "),a("p",[t._v("Although this is a valid construction:")]),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("bar")]),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(" "),a("span",{pre:!0,attrs:{class:"token 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class constants, you'll get an error:")]),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("bar")]),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(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),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 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("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")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("bar")]),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("// Error: Constant expression contains invalid operations")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),a("p",[t._v("But you can do:")]),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("bar")]),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(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),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 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 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constant"}},[t._v("BAR")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// OK")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),a("p",[t._v("For more information, see "),a("a",{attrs:{href:"http://php.net/manual/en/language.constants.php",target:"_blank",rel:"noopener noreferrer"}},[t._v("constants in the manual"),a("OutboundLink")],1),t._v(".")]),t._v(" "),a("h3",{attrs:{id:"using-class-to-retrieve-class-s-name"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#using-class-to-retrieve-class-s-name"}},[t._v("#")]),t._v(" Using ::class to retrieve class's name")]),t._v(" "),a("p",[t._v("PHP 5.5 introduced the "),a("code",[t._v("::class")]),t._v(" syntax to retrieve the full class name, taking namespace scope and "),a("code",[t._v("use")]),t._v(" statements into account.")]),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("namespace")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token package"}},[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("use")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token package"}},[t._v("bar"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("Bar")]),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 function"}},[t._v("json_encode")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("Bar")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token 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"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("json_encode")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token class-name class-name-fully-qualified static-context"}},[a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("Foo")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("class")]),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('// "Foo"')]),t._v("\n\n")])])]),a("p",[t._v("The above works even if the classes are not even defined (i.e. this code snippet works alone).")]),t._v(" "),a("p",[t._v("This syntax is useful for functions that require a class name. For example, it can be used with "),a("code",[t._v("class_exists")]),t._v(" to check a class exists. No errors will be generated regardless of return value in this snippet:")]),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("class_exists")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token class-name class-name-fully-qualified static-context"}},[t._v("ThisClass"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("Will"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("NeverBe"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("Loaded")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("class")]),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("h2",{attrs:{id:"abstract-classes"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#abstract-classes"}},[t._v("#")]),t._v(" Abstract Classes")]),t._v(" "),a("p",[t._v("An abstract class is a class that cannot be instantiated. Abstract classes can define abstract methods, which are methods without any body, only a definition:")]),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("abstract")]),t._v(" "),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("MyAbstractClass")]),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("abstract")]),t._v(" "),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("doSomething")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$a")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$b")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),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("Abstract classes should be extended by a child class which can then provide the implementation of these abstract methods.")]),t._v(" "),a("p",[t._v('The main purpose of a class like this is to provide a kind of template that allows children classes to inherit from, "forcing" a structure to adhere to. Lets elaborate on this with an example:')]),t._v(" "),a("p",[t._v("In this example we will be implementing a "),a("code",[t._v("Worker")]),t._v(" interface. First we define the 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("Worker")]),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("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("run")]),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("To ease the development of further Worker implementations, we will create an abstract worker class\nthat already provides the "),a("code",[t._v("run()")]),t._v(" method from the interface, but specifies some abstract methods that need to be filled in by any child 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("abstract")]),t._v(" "),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("AbstractWorker")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("implements")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Worker")]),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("protected")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token 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No error handling is needed in the "),a("code",[t._v("TransactionProcessorWorker")]),t._v(" because that is handled in the "),a("code",[t._v("AbsractWorker")]),t._v(".")]),t._v(" "),a("h3",{attrs:{id:"important-note"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#important-note"}},[t._v("#")]),t._v(" Important Note")]),t._v(" "),a("blockquote"),t._v(" "),a("p",[t._v("When inheriting from an abstract class, all methods marked abstract in\nthe parent's class declaration must be defined by the child (or the child itself\nmust also be marked abstract);\nadditionally, these methods must be defined with the same (or a less\nrestricted) visibility. For example, if the abstract method is defined\nas protected, the function implementation must be defined as either\nprotected or public, but not private.")]),t._v(" "),a("p",[a("sup",[a("strong",[t._v("Taken from the "),a("a",{attrs:{href:"http://php.net/manual/en/language.oop5.abstract.php",target:"_blank",rel:"noopener noreferrer"}},[t._v("PHP Documentation for Class Abstraction"),a("OutboundLink")],1),t._v(".")])])]),t._v(" "),a("p",[t._v("If you "),a("strong",[t._v("do not")]),t._v(" define the parent abstract classes methods within the child class, you will be thrown a "),a("strong",[t._v("Fatal PHP Error")]),t._v(" like the following.")]),t._v(" "),a("blockquote"),t._v(" "),a("p",[t._v("**Fatal error:** Class X contains 1 abstract method and must therefore\nbe declared abstract or implement the remaining methods (X::x)\nin")]),t._v(" "),a("h2",{attrs:{id:"late-static-binding"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#late-static-binding"}},[t._v("#")]),t._v(" Late static binding")]),t._v(" "),a("p",[t._v("In PHP 5.3+ and above you can utilize "),a("a",{attrs:{href:"http://php.net/manual/en/language.oop5.late-static-bindings.php",target:"_blank",rel:"noopener noreferrer"}},[t._v("late static binding"),a("OutboundLink")],1),t._v(" to control which class a static property or method is called from. It was added to overcome the problem inherent with the "),a("code",[t._v("self::")]),t._v(" scope resolutor. Take the following code")]),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("Horse")]),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("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),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("whatToSay")]),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("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'Neigh!'")]),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("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),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("speak")]),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 static-context"}},[t._v("self")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("whatToSay")]),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"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),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("MrEd")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("extends")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Horse")]),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("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),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("whatToSay")]),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("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'Hello Wilbur!'")]),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("p",[t._v("You would expect that the "),a("code",[t._v("MrEd")]),t._v(" class will override the parent "),a("code",[t._v("whatToSay()")]),t._v(" function. But when we run this we get something unexpected")]),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 class-name static-context"}},[t._v("Horse")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("speak")]),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("// Neigh!")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("MrEd")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("speak")]),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("// Neigh!")]),t._v("\n\n")])])]),a("p",[t._v("The problem is that "),a("code",[t._v("self::whatToSay();")]),t._v(" can only refer to the "),a("code",[t._v("Horse")]),t._v(" class, meaning it doesn't obey "),a("code",[t._v("MrEd")]),t._v(". If we switch to the "),a("code",[t._v("static::")]),t._v(" scope resolutor, we don't have this problem. This newer method tells the class to obey the instance calling it. Thus we get the inheritance we're expecting")]),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("Horse")]),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("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),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("whatToSay")]),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("echo")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'Neigh!'")]),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("public")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),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("speak")]),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 static-context"}},[t._v("static")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("whatToSay")]),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("// Late Static Binding")]),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 class-name static-context"}},[t._v("Horse")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("speak")]),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("// Neigh!")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token class-name static-context"}},[t._v("MrEd")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("speak")]),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("// Hello Wilbur!")]),t._v("\n\n")])])]),a("h2",{attrs:{id:"namespacing-and-autoloading"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#namespacing-and-autoloading"}},[t._v("#")]),t._v(" Namespacing and Autoloading")]),t._v(" "),a("p",[t._v("Technically, autoloading works by executing a callback when a PHP class is required but not found. Such callbacks usually attempt to load these classes.")]),t._v(" "),a("p",[t._v("Generally, autoloading can be understood as the attempt to load PHP files (especially PHP class files, where a PHP source file is dedicated for a specific class) from appropriate paths according to the class's fully-qualified name (FQN) when a class is needed.")]),t._v(" "),a("p",[t._v("Suppose we have these classes:")]),t._v(" "),a("p",[t._v("Class file for "),a("code",[t._v("application\\controllers\\Base")]),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"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("namespace")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token package"}},[t._v("application"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("controllers")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),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("Base")]),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 punctuation"}},[t._v("}")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])])]),a("p",[t._v("Class file for "),a("code",[t._v("application\\controllers\\Control")]),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"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("namespace")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token package"}},[t._v("application"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("\\")]),t._v("controllers")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),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("Control")]),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 punctuation"}},[t._v("}")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])])]),a("p",[t._v("Class file for "),a("code",[t._v("application\\models\\Page")]),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 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respectively:")]),t._v(" "),a("li",[t._v("Source folder\n"),a("ul",[a("li",[t._v("`applications`\n"),a("ul",[a("li",[t._v("`controllers`\n"),a("ul",[t._v("\n- `Base.php`\n- `Control.php`\n"),a("ul",[a("li",[a("code",[t._v("Page.php")])])]),t._v(" "),a("p",[t._v("This approach makes it possible to programmatically resolve the class file path according to the FQN, using this 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 keyword"}},[t._v("function")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function-definition function"}},[t._v("getClassPath")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token keyword type-hint"}},[t._v("string")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$sourceFolder")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword type-hint"}},[t._v("string")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$className")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword type-hint"}},[t._v("string")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$extension")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string double-quoted-string"}},[t._v('".php"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$sourceFolder")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(".")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string 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Any method not implemented in the base class must then be implemented by the concrete class that extends 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("abstract")]),t._v(" "),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("AbstractBaz")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("implements")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Foo")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" Bar "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Partial implementation of the required interface...")]),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("doSomething")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$param1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$param2")]),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 comment"}},[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 keyword"}},[t._v("class")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name-definition class-name"}},[t._v("Baz")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("extends")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("AbstractBaz")]),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("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("doAnotherThing")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$param1")]),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 comment"}},[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("p",[t._v("Notice that interface realization is an inherited characteristic. 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Use the keyword "),a("code",[t._v("const")]),t._v(" instead.")]),t._v(" "),a("p",[a("strong",[t._v("Why do I have to use "),a("code",[t._v("final")]),t._v("?")])]),t._v(" "),a("ol",[a("li",[t._v("Preventing massive inheritance chain of doom")]),t._v(" "),a("li",[t._v("Encouraging composition")]),t._v(" "),a("li",[t._v("Force the developer to think about user public API")]),t._v(" "),a("li",[t._v("Force the developer to shrink an object's public API")]),t._v(" "),a("li",[t._v("A "),a("code",[t._v("final")]),t._v(" class can always be made extensible")]),t._v(" "),a("li",[a("code",[t._v("extends")]),t._v(" breaks encapsulation")]),t._v(" "),a("li",[t._v("You don't need that flexibility")]),t._v(" "),a("li",[t._v("You are free to change the code")])]),t._v(" "),a("p",[a("strong",[t._v("When to avoid "),a("code",[t._v("final")]),t._v(":")]),t._v("\nFinal classes only work effectively under following assumptions:")]),t._v(" "),a("ol",[a("li",[t._v("There is an abstraction (interface) that the final class implements")]),t._v(" "),a("li",[t._v("All of the public API of the final class is part of that interface")])]),t._v(" "),a("h2",{attrs:{id:"autoloading"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#autoloading"}},[t._v("#")]),t._v(" Autoloading")]),t._v(" "),a("p",[t._v("Nobody wants to "),a("code",[t._v("require")]),t._v(" or "),a("code",[t._v("include")]),t._v(" every time a class or inheritance is used. Because it can be painful and is easy to forget, PHP is offering so called autoloading. If you are already using Composer, read about "),a("a",{attrs:{href:"https://stackoverflow.com/documentation/php/1053/composer/3397/autoloading-with-composer#t=201607252107257288764",target:"_blank",rel:"noopener noreferrer"}},[t._v("autoloading using Composer"),a("OutboundLink")],1),t._v(".")]),t._v(" "),a("p",[a("strong",[t._v("What exactly is autoloading?")])]),t._v(" "),a("p",[t._v("The name basically says it all. You do not have to get the file where the requested class is stored in, but PHP "),a("strong",[t._v("auto")]),t._v("matically "),a("strong",[t._v("load")]),t._v("s it.")]),t._v(" "),a("p",[a("strong",[t._v("How can I do this in basic PHP without third party code?")])]),t._v(" "),a("p",[t._v("There is the function "),a("a",{attrs:{href:"https://secure.php.net/manual/function.autoload.php",target:"_blank",rel:"noopener noreferrer"}},[a("code",[t._v("__autoload")]),a("OutboundLink")],1),t._v(", but it is considered better practice to use "),a("a",{attrs:{href:"https://secure.php.net/manual/function.spl-autoload-register.php",target:"_blank",rel:"noopener noreferrer"}},[a("code",[t._v("spl_autoload_register")]),a("OutboundLink")],1),t._v(". These functions will be considered by PHP every time a class is not defined within the given space. So adding autoload to an existing project is no problem, as defined classes (via "),a("code",[t._v("require")]),t._v(" i.e.) will work like before. 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If "),a("code",[t._v("FooBar")]),t._v(" needs to be loaded, it looks if "),a("code",[t._v("FooBar.php")]),t._v(" exists and if so includes it.")]),t._v(" "),a("p",[t._v("Of course this can be extended to fit the project's individual need. If "),a("code",[t._v("_")]),t._v(" inside a class name is used to group, e.g. "),a("code",[t._v("User_Post")]),t._v(" and "),a("code",[t._v("User_Image")]),t._v(" both refer to "),a("code",[t._v("User")]),t._v(', both classes can be kept in a folder called "User" like so:')]),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("spl_autoload_register")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$className")]),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 comment"}},[t._v("//                        replace _ by / or \\ (depending on OS)")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$path")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("sprintf")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'%s.php'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("str_replace")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string single-quoted-string"}},[t._v("'_'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token constant"}},[t._v("DIRECTORY_SEPARATOR")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$className")]),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 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 function"}},[t._v("file_exists")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$path")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("include")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$path")]),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(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("else")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// file not found")]),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("}")]),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("The class "),a("code",[t._v("User_Post")]),t._v(' will now be loaded from "User/Post.php", etc.')]),t._v(" "),a("p",[a("code",[t._v("spl_autoload_register")]),t._v(' can be tailored to various needs. 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No problem either.')]),t._v(" "),a("p",[t._v("If you want a more elaborate autoloading mechanism - and still don't want to include Composer - you can work without adding third party libraries.")]),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("spl_autoload_register")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$className")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token variable"}},[t._v("$path")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" 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Since this is static this reference is shared across ALL objects of this type.")]),t._v(" "),a("p",[t._v("The "),a("code",[t._v("getInstance()")]),t._v("method uses a method know as lazy instantiation to delay creating the object to the last possible moment as you do not want to have unused objects lying around in memory never intended to be used. It also saves time and CPU on page load not having to load more objects than necessary. The method is checking if the object is set, creating it if not, and returning it. This ensures that only one object of this kind is ever created.")]),t._v(" "),a("p",[t._v("We are also setting the constructor to be private to ensure that no one creates it with the "),a("code",[t._v("new")]),t._v(" keyword from the outside. If you need to inherit from this class just change the "),a("code",[t._v("private")]),t._v(" keywords to "),a("code",[t._v("protected")]),t._v(".")]),t._v(" "),a("p",[t._v("To use this object you just write the following:")]),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("$singleton")]),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("Singleton")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("getInstance")]),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("p",[t._v("Now I DO implore you to use dependency injection where you can and aim for loosely coupled objects, but sometimes that is just not reasonable and the singleton pattern can be of use.")]),t._v(" "),a("h2",{attrs:{id:"defining-a-basic-class"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#defining-a-basic-class"}},[t._v("#")]),t._v(" Defining a Basic Class")]),t._v(" "),a("p",[t._v("An object in PHP contains variables and functions. 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