mirror of
https://github.com/sigmasternchen/php-doc-en
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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@322134 c90b9560-bf6c-de11-be94-00142212c4b1
372 lines
10 KiB
XML
372 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.overloading" xmlns="http://docbook.org/ns/docbook">
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<title>Overloading</title>
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<para>
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Overloading in PHP provides means to dynamically
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<quote>create</quote> properties and methods.
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These dynamic entities are processed via magic methods
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one can establish in a class for various action types.
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</para>
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<para>
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The overloading methods are invoked when interacting with
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properties or methods that have not been declared or are not
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<link linkend="language.oop5.visibility">visible</link> in
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the current scope. The rest of this section will use the terms
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<quote>inaccessible properties</quote> and <quote>inaccessible
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methods</quote> to refer to this combination of declaration
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and visibility.
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</para>
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<para>
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All overloading methods must be defined as <literal>public</literal>.
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</para>
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<note>
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<para>
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None of the arguments of these magic methods can be
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<link linkend="functions.arguments.by-reference">passed by
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reference</link>.
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</para>
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</note>
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<note>
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<para>
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PHP's interpretation of <quote>overloading</quote> is
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different than most object oriented languages. Overloading
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traditionally provides the ability to have multiple methods
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with the same name but different quantities and types of
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arguments.
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</para>
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</note>
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<sect2 xml:id="language.oop5.overloading.changelog">
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&reftitle.changelog;
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<para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>5.3.0</entry>
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<entry>
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Added <link linkend="object.callstatic">__callStatic()</link>.
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Added warning to enforce public visibility and non-static declaration.
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</entry>
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</row>
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<row>
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<entry>5.1.0</entry>
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<entry>
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Added <link linkend="object.isset">__isset()</link> and <link linkend="object.unset">__unset()</link>.
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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</sect2>
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<sect2 xml:id="language.oop5.overloading.members">
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<title>Property overloading</title>
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<methodsynopsis xml:id="object.set">
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<modifier>public</modifier> <type>void</type><methodname>__set</methodname>
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<methodparam><type>string</type><parameter>name</parameter></methodparam>
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<methodparam><type>mixed</type><parameter>value</parameter></methodparam>
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</methodsynopsis>
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<methodsynopsis xml:id="object.get">
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<modifier>public</modifier> <type>mixed</type><methodname>__get</methodname>
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<methodparam><type>string</type><parameter>name</parameter></methodparam>
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</methodsynopsis>
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<methodsynopsis xml:id="object.isset">
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<modifier>public</modifier> <type>bool</type><methodname>__isset</methodname>
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<methodparam><type>string</type><parameter>name</parameter></methodparam>
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</methodsynopsis>
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<methodsynopsis xml:id="object.unset">
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<modifier>public</modifier> <type>void</type><methodname>__unset</methodname>
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<methodparam><type>string</type><parameter>name</parameter></methodparam>
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</methodsynopsis>
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<para>
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<link linkend="object.set">__set()</link> is run when writing data to
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inaccessible properties.
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</para>
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<para>
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<link linkend="object.get">__get()</link> is utilized for reading data from
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inaccessible properties.
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</para>
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<para>
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<link linkend="object.isset">__isset()</link> is triggered by calling
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<function>isset</function> or <function>empty</function>
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on inaccessible properties.
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</para>
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<para>
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<link linkend="object.unset">__unset()</link> is invoked when
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<function>unset</function> is used on inaccessible properties.
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</para>
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<para>
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The <varname>$name</varname> argument is the name of the
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property being interacted with. The <link linkend="object.set">__set()</link>
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method's <varname>$value</varname> argument specifies the
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value the <varname>$name</varname>'ed property should be set
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to.
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</para>
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<para>
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Property overloading only works in object context. These magic
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methods will not be triggered in static context. Therefore
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these methods should not be declared
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<link linkend="language.oop5.static">static</link>. As of PHP
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5.3.0, a warning is issued if one of the magic overloading
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methods is declared <literal>static</literal>.
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</para>
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<note>
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<para>
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The return value of <link linkend="object.set">__set()</link> is ignored
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because of the way PHP processes the assignment operator.
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Similarly, <link linkend="object.get">__get()</link> is never called when
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chaining assignments together like this:
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<literal><![CDATA[ $a = $obj->b = 8; ]]></literal>
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</para>
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</note>
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<note>
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<para>
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It is not possible to use overloaded properties in other
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language constructs than <function>isset</function>. This
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means if <function>empty</function> is called on an overloaded
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property, the overloaded method is not called.
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</para>
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<para>
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To workaround that limitation, the overloaded property must
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be copied into a local variable in the scope and then be
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handed to <function>empty</function>.
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</para>
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</note>
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<example>
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<title>
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Overloading properties via the <link linkend="object.get">__get()</link>,
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<link linkend="object.set">__set()</link>, <link linkend="object.isset">__isset()</link>
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and <link linkend="object.unset">__unset()</link> methods
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</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class PropertyTest
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{
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/** Location for overloaded data. */
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private $data = array();
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/** Overloading not used on declared properties. */
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public $declared = 1;
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/** Overloading only used on this when accessed outside the class. */
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private $hidden = 2;
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public function __set($name, $value)
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{
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echo "Setting '$name' to '$value'\n";
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$this->data[$name] = $value;
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}
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public function __get($name)
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{
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echo "Getting '$name'\n";
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if (array_key_exists($name, $this->data)) {
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return $this->data[$name];
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}
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$trace = debug_backtrace();
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trigger_error(
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'Undefined property via __get(): ' . $name .
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' in ' . $trace[0]['file'] .
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' on line ' . $trace[0]['line'],
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E_USER_NOTICE);
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return null;
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}
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/** As of PHP 5.1.0 */
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public function __isset($name)
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{
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echo "Is '$name' set?\n";
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return isset($this->data[$name]);
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}
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/** As of PHP 5.1.0 */
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public function __unset($name)
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{
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echo "Unsetting '$name'\n";
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unset($this->data[$name]);
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}
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/** Not a magic method, just here for example. */
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public function getHidden()
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{
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return $this->hidden;
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}
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}
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echo "<pre>\n";
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$obj = new PropertyTest;
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$obj->a = 1;
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echo $obj->a . "\n\n";
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var_dump(isset($obj->a));
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unset($obj->a);
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var_dump(isset($obj->a));
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echo "\n";
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echo $obj->declared . "\n\n";
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echo "Let's experiment with the private property named 'hidden':\n";
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echo "Privates are visible inside the class, so __get() not used...\n";
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echo $obj->getHidden() . "\n";
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echo "Privates not visible outside of class, so __get() is used...\n";
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echo $obj->hidden . "\n";
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen role="php">
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<![CDATA[
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Setting 'a' to '1'
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Getting 'a'
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1
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Is 'a' set?
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bool(true)
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Unsetting 'a'
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Is 'a' set?
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bool(false)
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1
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Let's experiment with the private property named 'hidden':
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Privates are visible inside the class, so __get() not used...
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2
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Privates not visible outside of class, so __get() is used...
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Getting 'hidden'
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Notice: Undefined property via __get(): hidden in <file> on line 70 in <file> on line 29
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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.overloading.methods">
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<title>Method overloading</title>
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<methodsynopsis xml:id="object.call">
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<modifier>public</modifier> <type>mixed</type><methodname>__call</methodname>
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<methodparam><type>string</type><parameter>name</parameter></methodparam>
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<methodparam><type>array</type><parameter>arguments</parameter></methodparam>
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</methodsynopsis>
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<methodsynopsis xml:id="object.callstatic">
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<modifier>public static</modifier> <type>mixed</type><methodname>__callStatic</methodname>
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<methodparam><type>string</type><parameter>name</parameter></methodparam>
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<methodparam><type>array</type><parameter>arguments</parameter></methodparam>
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</methodsynopsis>
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<para>
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<link linkend="object.call">__call()</link> is triggered when invoking
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inaccessible methods in an object context.
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</para>
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<para>
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<link linkend="object.callstatic">__callStatic()</link> is triggered when invoking
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inaccessible methods in a static context.
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</para>
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<para>
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The <varname>$name</varname> argument is the name of the
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method being called. The <varname>$arguments</varname>
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argument is an enumerated array containing the parameters
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passed to the <varname>$name</varname>'ed method.
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</para>
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<example>
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<title>
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Overloading methods via the <link linkend="object.call">__call()</link>
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and <link linkend="object.callstatic">__callStatic()</link> methods
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</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class MethodTest
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{
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public function __call($name, $arguments)
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{
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// Note: value of $name is case sensitive.
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echo "Calling object method '$name' "
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. implode(', ', $arguments). "\n";
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}
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/** As of PHP 5.3.0 */
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public static function __callStatic($name, $arguments)
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{
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// Note: value of $name is case sensitive.
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echo "Calling static method '$name' "
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. implode(', ', $arguments). "\n";
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}
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}
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$obj = new MethodTest;
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$obj->runTest('in object context');
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MethodTest::runTest('in static context'); // As of PHP 5.3.0
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen role="php">
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<![CDATA[
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Calling object method 'runTest' in object context
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Calling static method 'runTest' in static context
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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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