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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.is-callable" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>is_callable</refname>
<refpurpose>
Verify that a value can be called as a function from the current scope
</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>bool</type><methodname>is_callable</methodname>
<methodparam><type>mixed</type><parameter>value</parameter></methodparam>
<methodparam choice="opt"><type>bool</type><parameter>syntax_only</parameter><initializer>&false;</initializer></methodparam>
<methodparam choice="opt"><type>string</type><parameter role="reference">callable_name</parameter><initializer>&null;</initializer></methodparam>
</methodsynopsis>
<para>
Verifies that <parameter>value</parameter> is a <type>callable</type>,
or that it can be called using the
<function>call_user_func</function> function.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>value</parameter></term>
<listitem>
<para>
The value to be checked.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>syntax_only</parameter></term>
<listitem>
<para>
If set to &true; the function only verifies that
<parameter>value</parameter> might be a function or method. It will
reject any values that are not <link linkend="object.invoke">invokable</link> objects,
<classname>Closure</classname>, &string;s, or &array;s that do not have
a valid structure to be used as a callback. A valid callable array
has 2 entries, the first of which is an object
or a string, and the second a string.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>callable_name</parameter></term>
<listitem>
<para>
Receives the "callable name", e.g.
<literal>"SomeClass::someMethod"</literal>. Note, however, that despite
the implication that <literal>SomeClass::someMethod()</literal> is a
callable static method, this is not the case.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns &true; if <parameter>value</parameter> is callable, &false;
otherwise.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title>Checking whether a string can be called as a function</title>
<programlisting role="php">
<![CDATA[
<?php
function someFunction() {}
$functionVariable = 'someFunction';
var_dump(is_callable($functionVariable, false, $callable_name));
var_dump($callable_name);
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
bool(true)
string(12) "someFunction"
]]>
</screen>
</example>
<example>
<title>Checking whether an array can be called as a function</title>
<programlisting role="php">
<![CDATA[
<?php
class SomeClass
{
public function someMethod() {}
}
$anObject = new SomeClass();
$methodVariable = [$anObject, 'someMethod'];
var_dump(is_callable($methodVariable, true, $callable_name));
var_dump($callable_name);
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
bool(true)
string(21) "SomeClass::someMethod"
]]>
</screen>
</example>
<example>
<title><function>is_callable</function> and constructors</title>
<simpara>
<function>is_callable</function> reports constructors as
not being callable.
</simpara>
<programlisting role="php">
<![CDATA[
<?php
class Foo
{
public function __construct() {}
public function foo() {}
}
var_dump(
is_callable(['Foo', '__construct']),
is_callable(['Foo', 'foo'])
);
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
bool(false)
bool(false)
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<simplelist>
<member>
An object is always callable if it implements <link linkend="object.invoke">__invoke()</link>,
and that method is visible in the current scope.
</member>
<member>
A class name is callable if it implements <link linkend="object.callstatic">__callStatic()</link>.
</member>
<member>
If an object implements <link linkend="object.call">__call()</link>, then this function will
return &true; for any method on that object, even if the method is not defined.
</member>
<member>
This function may trigger autoloading if called with the name of a class.
</member>
</simplelist>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>call_user_func</function></member>
<member><function>function_exists</function></member>
<member><function>method_exists</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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