reference/var/functions/is-callable.xml
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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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Verify that a value is a <type>callable</type>.
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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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<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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<parameter>value</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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<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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]]>
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</programlisting>
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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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<function>is_callable</function> reports constructors as
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not being callable.
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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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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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var_dump(
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is_callable(array('Foo', '__construct')),
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is_callable(array('Foo', 'foo'))
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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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]]>
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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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</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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