ob-list-handlers.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.ob-list-handlers">
 <refnamediv>
  <refname>ob_list_handlers</refname>
  <refpurpose>List all output handlers in use</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>array</type><methodname>ob_list_handlers</methodname>
   <void/>
  </methodsynopsis>
  <para>
   Lists all output handlers in use.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  &no.function.parameters;
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   This will return an array with the output handlers in use (if any).
  </para>
  <para>
   If <link linkend="ini.output-buffering">output_buffering</link> is enabled
   and no <link linkend="ini.output-handler">output_handler</link> is set,
   or no callback or &null; was passed to <function>ob_start</function>,
   <literal>"default output handler"</literal> is returned.
   Enabling <link linkend="ini.output-buffering">output_buffering</link>
   and setting an <link linkend="ini.output-handler">output_handler</link>
   is equivalent to passing
   an <link linkend="functions.internal">internal (built-in) function</link>
   to <function>ob_start</function>.
  </para>
  <para>
   If a <type>callable</type> was passed to <function>ob_start</function>,
   the <link linkend="language.namespaces.basics">fully qualified name</link>
   of the <type>callable</type> is returned.
   If the <type>callable</type> is an object implementing
   <link linkend="language.oop5.magic.invoke">__invoke()</link>,
   the <link linkend="language.namespaces.basics">fully qualified name</link>
   of the object's <link linkend="language.oop5.magic.invoke">__invoke()</link>
   method is returned.
   If the <type>callable</type> is a <classname>Closure</classname>,
   <literal>"Closure::__invoke"</literal> is returned.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>ob_list_handlers</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// using output_buffering=On, no output_handler set
var_dump(ob_list_handlers());
ob_end_flush();

// no callback or null
ob_start();
var_dump(ob_list_handlers());
ob_end_flush();

// anonymous function
ob_start(function($string) { return $string; });
var_dump(ob_list_handlers());
ob_end_flush();

// arrow function
ob_start(fn($string) => $string);
var_dump(ob_list_handlers());
ob_end_flush();

// first class callable
$firstClassCallable = userDefinedFunction(...);

ob_start([$firstClassCallable, '__invoke']);
var_dump(ob_list_handlers());
ob_end_flush();

// internal (built-in) function
ob_start('print_r');
var_dump(ob_list_handlers());
ob_end_flush();

// user-defined function
function userDefinedFunction($string, $flags) { return $string; };

ob_start('userDefinedFunction');
var_dump(ob_list_handlers());
ob_end_flush();

class MyClass {
    public static function staticHandle($string) {
        return $string;
    }

    public static function handle($string) {
        return $string;
    }

    public function __invoke($string) {
        return $string;
    }
}

// class and static method
ob_start(['MyClass','staticHandle']);
var_dump(ob_list_handlers());
ob_end_flush();

// object and non-static method
ob_start([new MyClass,'handle']);
var_dump(ob_list_handlers());
ob_end_flush();

// invokable object
ob_start(new MyClass);
var_dump(ob_list_handlers());
ob_end_flush();
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
array(1) {
  [0]=>
  string(22) "default output handler"
}
array(1) {
  [0]=>
  string(22) "default output handler"
}
array(1) {
  [0]=>
  string(7) "print_r"
}
array(1) {
  [0]=>
  string(19) "userDefinedFunction"
}
array(1) {
  [0]=>
  string(17) "Closure::__invoke"
}
array(1) {
  [0]=>
  string(17) "Closure::__invoke"
}
array(1) {
  [0]=>
  string(17) "Closure::__invoke"
}
array(1) {
  [0]=>
  string(21) "MyClass::staticHandle"
}
array(1) {
  [0]=>
  string(15) "MyClass::handle"
}
array(1) {
  [0]=>
  string(17) "MyClass::__invoke"
}
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>ob_end_clean</function></member>
    <member><function>ob_end_flush</function></member>
    <member><function>ob_get_flush</function></member>
    <member><function>ob_start</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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