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Document dynamic access of static methods/constants/members
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@244547 c90b9560-bf6c-de11-be94-00142212c4b1
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3 changed files with 32 additions and 9 deletions
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.10 $ -->
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<!-- $Revision: 1.11 $ -->
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<sect1 xml:id="language.oop5.constants" xmlns="http://docbook.org/ns/docbook">
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<title>Class Constants</title>
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<para>
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It is possible to define constant values on a per-class basis remaining the
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same and unchangeable. Constants differ from normal variables in that you
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don't use the <varname>$</varname> symbol to declare or use them. Like
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<link linkend="language.oop5.static">static</link> members, constant values
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cannot be accessed from an instance of the object (using
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<literal>$object::constant</literal>).
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don't use the <varname>$</varname> symbol to declare or use them.
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</para>
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<para>
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The value must be a constant expression, not (for example) a variable, a
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class member, result of a mathematical operation or a function call.
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</para>
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<para>
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As of PHP 5.3.0, it's possible to reference the class using a variable.
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</para>
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<example>
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<title>Defining and using a constant</title>
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<programlisting role="php">
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@ -31,9 +32,13 @@ class MyClass
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echo MyClass::constant . "\n";
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$classname = "MyClass";
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echo $classname::constant . "\n";
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$class = new MyClass();
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$class->showConstant();
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// echo $class::constant; is not allowed
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echo $class::constant."\n";
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?>
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]]>
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</programlisting>
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.10 $ -->
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<!-- $Revision: 1.11 $ -->
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<sect1 xml:id="language.oop5.paamayim-nekudotayim" xmlns="http://docbook.org/ns/docbook">
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<title>Scope Resolution Operator (::)</title>
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the name of the class.
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</para>
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<para>
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As of PHP 5.3.0, it's possible to reference the class using a variable.
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</para>
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<para>
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Paamayim Nekudotayim would, at first, seem like a strange choice for
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naming a double-colon. However, while writing the Zend Engine 0.5
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const CONST_VALUE = 'A constant value';
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}
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$classname = 'MyClass';
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echo $classname::CONST_VALUE;
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echo MyClass::CONST_VALUE;
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?>
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]]>
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@ -58,6 +65,9 @@ class OtherClass extends MyClass
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}
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}
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$classname = 'OtherClass';
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echo $classname::doubleColon();
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OtherClass::doubleColon();
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?>
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]]>
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.13 $ -->
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<!-- $Revision: 1.14 $ -->
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<sect1 xml:id="language.oop5.static" xmlns="http://docbook.org/ns/docbook">
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<title>Static Keyword</title>
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Calling non-static methods statically generates an E_STRICT level warning.
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</para>
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<para>
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As of PHP 5.3.0, it's possible to reference the class using a variable.
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</para>
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<example>
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<title>Static member example</title>
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<programlisting role="php">
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print $foo->staticValue() . "\n";
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print $foo->my_static . "\n"; // Undefined "Property" my_static
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// $foo::my_static is not possible
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print $foo::$my_static . "\n";
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$classname = 'Foo';
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print $classname::$my_static . "\n";
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print Bar::$my_static . "\n";
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$bar = new Bar();
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}
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Foo::aStaticMethod();
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$classname = 'Foo';
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$classname::aStaticMethod();
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?>
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]]>
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</programlisting>
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