reference/var/functions/is-callable.xml
32c55286c8739fd20de9c8624473b2f3268de68e
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<refnamediv>
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<refname>is_callable</refname>
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<refpurpose>
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Verify that the contents of a variable can be called as a function
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Verify that a value can be called as a function from the current scope
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</refpurpose>
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</refnamediv>
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&reftitle.description;
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<methodsynopsis>
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<type>bool</type><methodname>is_callable</methodname>
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<methodparam><type>mixed</type><parameter>var</parameter></methodparam>
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<methodparam choice="opt"><type>bool</type><parameter>syntax_only</parameter><initializer>false</initializer></methodparam>
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<methodparam choice="opt"><type>string</type><parameter role="reference">callable_name</parameter></methodparam>
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<methodparam><type>mixed</type><parameter>value</parameter></methodparam>
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<methodparam choice="opt"><type>bool</type><parameter>syntax_only</parameter><initializer>&false;</initializer></methodparam>
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<methodparam choice="opt"><type>string</type><parameter role="reference">callable_name</parameter><initializer>&null;</initializer></methodparam>
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</methodsynopsis>
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<para>
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Verify that the contents of a variable can be called as a function.
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This can check that a simple variable contains the name of a valid
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function, or that an array contains a properly encoded object and
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function name.
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Verifies that <parameter>value</parameter> is a <type>callable</type>,
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or that it can be called using the
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<function>call_user_func</function> function.
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</para>
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</refsect1>
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>var</parameter></term>
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<term><parameter>value</parameter></term>
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<listitem>
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<para>
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The value to check
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The value to be checked.
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</para>
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</listitem>
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</varlistentry>
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<listitem>
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<para>
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If set to &true; the function only verifies that
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<parameter>name</parameter> might be a function or method. It will only
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reject simple variables that are not strings, or an array that does
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not have a valid structure to be used as a callback. The valid ones
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are supposed to have only 2 entries, the first of which is an object
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<parameter>value</parameter> might be a function or method. It will
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reject any values that are not <link linkend="object.invoke">invokable</link> objects,
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<classname>Closure</classname>, &string;s, or &array;s that do not have
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a valid structure to be used as a callback. A valid callable array
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has 2 entries, the first of which is an object
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or a string, and the second a string.
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</para>
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</listitem>
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<term><parameter>callable_name</parameter></term>
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<listitem>
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<para>
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Receives the "callable name". In the example below it is
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"someClass::someMethod". Note, however, that despite the implication
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that someClass::SomeMethod() is a callable static method, this is not
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the case.
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Receives the "callable name", e.g.
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<literal>"SomeClass::someMethod"</literal>. Note, however, that despite
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the implication that <literal>SomeClass::someMethod()</literal> is a
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callable static method, this is not the case.
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</para>
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</listitem>
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</varlistentry>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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Returns &true; if <parameter>var</parameter> is callable, &false;
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Returns &true; if <parameter>value</parameter> is callable, &false;
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otherwise.
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</para>
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</refsect1>
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&reftitle.examples;
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<para>
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<example>
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<title><function>is_callable</function> example</title>
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<title>Checking whether a string can be called as a function</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// How to check a variable to see if it can be called
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// as a function.
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//
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// Simple variable containing a function
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//
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function someFunction() {}
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function someFunction()
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$functionVariable = 'someFunction';
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var_dump(is_callable($functionVariable, false, $callable_name));
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var_dump($callable_name);
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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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bool(true)
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string(12) "someFunction"
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]]>
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</screen>
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</example>
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<example>
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<title>Checking whether an array can be called as a function</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class SomeClass
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{
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public function someMethod() {}
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}
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$functionVariable = 'someFunction';
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$anObject = new SomeClass();
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var_dump(is_callable($functionVariable, false, $callable_name)); // bool(true)
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$methodVariable = [$anObject, 'someMethod'];
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echo $callable_name, "\n"; // someFunction
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var_dump(is_callable($methodVariable, true, $callable_name));
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//
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// Array containing a method
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//
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var_dump($callable_name);
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class someClass {
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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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bool(true)
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string(21) "SomeClass::someMethod"
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]]>
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</screen>
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</example>
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<example>
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<title><function>is_callable</function> and constructors</title>
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<simpara>
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Despite the fact that constructors are the methods that are called when
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an object is created, they are not static methods and
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<function>is_callable</function> will return &false; for them. It's not
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possible to use <function>is_callable</function> to check if a class can
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be instantiated from the current scope.
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</simpara>
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<programlisting role="php">
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<![CDATA[
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<?php
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function someMethod()
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{
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}
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class Foo
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{
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public function __construct() {}
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public function foo() {}
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}
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$anObject = new someClass();
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$methodVariable = array($anObject, 'someMethod');
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var_dump(
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is_callable(['Foo', '__construct']),
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is_callable(['Foo', 'foo'])
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);
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var_dump(is_callable($methodVariable, true, $callable_name)); // bool(true)
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echo $callable_name, "\n"; // someClass::someMethod
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$foo = new Foo();
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var_dump(is_callable([$foo, '__construct']));
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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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bool(false)
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bool(false)
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bool(true)
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]]>
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</screen>
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</example>
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</para>
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</refsect1>
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<refsect1 role="notes">
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&reftitle.notes;
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<simplelist>
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<member>
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An object is always callable if it implements <link linkend="object.invoke">__invoke()</link>,
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and that method is visible in the current scope.
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</member>
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<member>
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A class name is callable if it implements <link linkend="object.callstatic">__callStatic()</link>.
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</member>
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<member>
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If an object implements <link linkend="object.call">__call()</link>, then this function will
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return &true; for any method on that object, even if the method is not defined.
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</member>
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<member>
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This function may trigger autoloading if called with the name of a class.
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</member>
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</simplelist>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>call_user_func</function></member>
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<member><function>function_exists</function></member>
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<member><function>method_exists</function></member>
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</simplelist>
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</refsect1>
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</refentry>
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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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Translation status