mirror of
https://github.com/sigmasternchen/php-doc-en
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4307b3bcdf
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@334638 c90b9560-bf6c-de11-be94-00142212c4b1
363 lines
10 KiB
XML
363 lines
10 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<sect1 xml:id="language.oop5.magic" xmlns="http://docbook.org/ns/docbook">
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<title>Magic Methods</title>
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<para>
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The function names
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<link linkend="object.construct">__construct()</link>,
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<link linkend="object.destruct">__destruct()</link>,
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<link linkend="object.call">__call()</link>,
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<link linkend="object.callstatic">__callStatic()</link>,
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<link linkend="object.get">__get()</link>,
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<link linkend="object.set">__set()</link>,
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<link linkend="object.isset">__isset()</link>,
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<link linkend="object.unset">__unset()</link>,
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<link linkend="object.sleep">__sleep()</link>,
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<link linkend="object.wakeup">__wakeup()</link>,
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<link linkend="object.tostring">__toString()</link>,
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<link linkend="object.invoke">__invoke()</link>,
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<link linkend="object.set-state">__set_state()</link>,
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<link linkend="object.clone">__clone()</link> and
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<link linkend="object.debuginfo">__debugInfo()</link>
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are magical in PHP classes. You
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cannot have functions with these names in any of your
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classes unless you want the magic functionality associated
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with them.
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</para>
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<caution>
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<simpara>
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PHP reserves all function names starting with __ as magical.
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It is recommended that you do not use function names with
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__ in PHP unless you want some documented magic functionality.
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</simpara>
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</caution>
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<sect2 xml:id="language.oop5.magic.sleep">
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<title>
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<link linkend="object.sleep">__sleep()</link> and
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<link linkend="object.wakeup">__wakeup()</link>
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</title>
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<methodsynopsis xml:id="object.sleep">
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<modifier>public</modifier> <type>array</type><methodname>__sleep</methodname>
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<void/>
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</methodsynopsis>
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<methodsynopsis xml:id="object.wakeup">
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<type>void</type><methodname>__wakeup</methodname>
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<void/>
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</methodsynopsis>
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<para>
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<function>serialize</function> checks if your class has a function with
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the magic name <link linkend="object.sleep">__sleep()</link>. If so, that function is
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executed prior to any serialization. It can clean up the object
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and is supposed to return an array with the names of all variables
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of that object that should be serialized.
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If the method doesn't return anything then &null; is serialized and
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<constant>E_NOTICE</constant> is issued.
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</para>
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<note>
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<para>
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It is not possible for <link linkend="object.sleep">__sleep()</link> to return names of
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private properties in parent classes. Doing this will result in an
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<constant>E_NOTICE</constant> level error. Instead you may use the
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<classname>Serializable</classname> interface.
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</para>
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</note>
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<para>
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The intended use of <link linkend="object.sleep">__sleep()</link> is to commit pending
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data or perform similar cleanup tasks. Also, the function is
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useful if you have very large objects which do not need to be
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saved completely.
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</para>
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<para>
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Conversely, <function>unserialize</function> checks for the
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presence of a function with the magic name
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<link linkend="object.wakeup">__wakeup()</link>. If present, this function can
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reconstruct any resources that the object may have.
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</para>
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<para>
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The intended use of <link linkend="object.wakeup">__wakeup()</link> is to
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reestablish any database connections that may have been lost
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during serialization and perform other reinitialization
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tasks.
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</para>
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<example>
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<title>Sleep and wakeup</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class Connection
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{
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protected $link;
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private $dsn, $username, $password;
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public function __construct($dsn, $username, $password)
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{
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$this->dsn = $dsn;
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$this->username = $username;
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$this->password = $password;
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$this->connect();
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}
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private function connect()
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{
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$this->link = new PDO($this->dsn, $this->username, $this->password);
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}
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public function __sleep()
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{
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return array('dsn', 'username', 'password');
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}
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public function __wakeup()
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{
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$this->connect();
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}
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}?>
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]]>
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</programlisting>
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</example>
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</sect2>
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<sect2 xml:id="language.oop5.magic.tostring">
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<title><link linkend="object.tostring">__toString()</link></title>
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<methodsynopsis xml:id="object.tostring">
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<modifier>public</modifier> <type>string</type><methodname>__toString</methodname>
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<void/>
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</methodsynopsis>
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<para>
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The <link linkend="object.tostring">__toString()</link> method allows a class to decide
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how it will react when it is treated like a string. For example,
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what <literal>echo $obj;</literal> will print. This method must
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return a string, as otherwise a fatal <constant>E_RECOVERABLE_ERROR</constant>
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level error is emitted.
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</para>
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<warning>
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<simpara>
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You cannot throw an exception from within a
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<link linkend="object.tostring">__toString()</link> method. Doing so will
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result in a fatal error.
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</simpara>
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</warning>
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<example>
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<title>Simple example</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// Declare a simple class
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class TestClass
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{
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public $foo;
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public function __construct($foo)
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{
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$this->foo = $foo;
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}
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public function __toString()
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{
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return $this->foo;
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}
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}
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$class = new TestClass('Hello');
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echo $class;
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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Hello
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]]>
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</screen>
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</example>
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<para>
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It is worth noting that before PHP 5.2.0 the <link linkend="object.tostring">__toString()</link>
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method was only called when it was directly combined with
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<function>echo</function> or <function>print</function>.
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Since PHP 5.2.0, it is called in any string context (e.g. in
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<function>printf</function> with <literal>%s</literal> modifier) but not
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in other types contexts (e.g. with <literal>%d</literal> modifier).
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Since PHP 5.2.0, converting objects without <link linkend="object.tostring">__toString()</link>
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method to string would cause <constant>E_RECOVERABLE_ERROR</constant>.
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</para>
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</sect2>
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<sect2 xml:id="language.oop5.magic.invoke">
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<title><link linkend="object.invoke">__invoke()</link></title>
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<methodsynopsis xml:id="object.invoke">
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<type>mixed</type><methodname>__invoke</methodname>
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<methodparam choice="opt"><parameter>...</parameter></methodparam>
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</methodsynopsis>
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<para>
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The <link linkend="object.invoke">__invoke()</link> method is called when a script tries to
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call an object as a function.
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</para>
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<note>
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<para>
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This feature is available since PHP 5.3.0.
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</para>
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</note>
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<example>
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<title>Using <link linkend="object.invoke">__invoke()</link></title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class CallableClass
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{
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public function __invoke($x)
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{
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var_dump($x);
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}
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}
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$obj = new CallableClass;
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$obj(5);
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var_dump(is_callable($obj));
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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int(5)
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bool(true)
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]]>
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</screen>
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</example>
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</sect2>
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<sect2 xml:id="language.oop5.magic.set-state">
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<title><link linkend="object.set-state">__set_state()</link></title>
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<methodsynopsis xml:id="object.set-state">
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<modifier>static</modifier> <type>object</type><methodname>__set_state</methodname>
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<methodparam><type>array</type><parameter>properties</parameter></methodparam>
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</methodsynopsis>
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<para>
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This <link linkend="language.oop5.static">static</link> method is called
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for classes exported by <function>var_export</function> since PHP 5.1.0.
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</para>
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<para>
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The only parameter of this method is an array containing exported
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properties in the form <literal>array('property' => value, ...)</literal>.
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</para>
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<example>
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<title>Using <link linkend="object.set-state">__set_state()</link> (since PHP 5.1.0)</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class A
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{
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public $var1;
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public $var2;
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public static function __set_state($an_array) // As of PHP 5.1.0
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{
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$obj = new A;
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$obj->var1 = $an_array['var1'];
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$obj->var2 = $an_array['var2'];
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return $obj;
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}
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}
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$a = new A;
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$a->var1 = 5;
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$a->var2 = 'foo';
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eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(
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// 'var1' => 5,
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// 'var2' => 'foo',
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// ));
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var_dump($b);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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object(A)#2 (2) {
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["var1"]=>
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int(5)
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["var2"]=>
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string(3) "foo"
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}
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]]>
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</screen>
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</example>
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</sect2>
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<sect2 xml:id="language.oop5.magic.debuginfo">
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<title><link linkend="object.debuginfo">__debugInfo()</link></title>
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<methodsynopsis xml:id="object.debuginfo">
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<type>array</type><methodname>__debugInfo</methodname>
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<void/>
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</methodsynopsis>
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<para>
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This method is called by <function>var_dump</function> when dumping an
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object to get the properties that should be shown. If the method isn't
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defined on an object, then all public, protected and private properties
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will be shown.
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</para>
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<para>
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This feature was added in PHP 5.6.0.
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</para>
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<example>
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<title>Using <link linkend="object.debuginfo">__debugInfo()</link></title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class C {
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private $prop;
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public function __construct($val) {
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$this->prop = $val;
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}
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public function __debugInfo() {
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return [
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'propSquared' => $this->prop ** 2,
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];
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}
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}
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var_dump(new C(42));
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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object(C)#1 (1) {
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["propSquared"]=>
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int(1764)
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}
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]]>
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</screen>
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</example>
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</sect2>
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</sect1>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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