IMPRESS dotted_line CONTACT dotted_line search dotted_line Kontakt dotted_line sitemap dotted_line print
108 PHP-Resource users online

Switch to another languags Deutsch aktuelle Sprache Englisch
php-resource

PHP Manual

Function handling Functions
PHP Manual

function_exists

(PHP 4, PHP 5)

function_exists — Return TRUE if the given function has been defined

Description

bool function_exists ( string $function_name )

Checks the list of defined functions, both built-in (internal) and user-defined, for function_name.

Parameters

function_name

The function name, as a string.

Return Values

Returns TRUE if function_name exists and is a function, FALSE otherwise.

Note:

This function will return FALSE for constructs, such as include_once and echo.

Examples

Example #1 function_exists() example

<?php
if (function_exists('imap_open')) {
    echo "IMAP functions are available.<br />\n";
} else {
    echo "IMAP functions are not available.<br />\n";
}
?>

Notes

Note:

A function name may exist even if the function itself is unusable due to configuration or compiling options (with the image functions being an example).

See Also

Function handling Functions
PHP Manual


Comments to the PHP manual
Write new comment
 

 
PHP-Index
  1. Introduction
  2. Installation and Configuration
  3. Language reference
  4. Security
  5. Features
  6. Function reference
  7. PHP and zend engine internal
  8. FAQ: Frequently Asked Questions
  9. Appendices



 

New Tutorial entries

Migration einer PHP 5 App auf PHP 7

Dieses PHP 7 Tutorial zeigt dir, wie du dein PHP5 Script auf PHP7 umstellst.

Berni | Category: PHP
PHP 7 Virtual Machine

Dieser Artikel zielt darauf ab, einen Überblick über die Zend Virtual Machine, wie es in PHP 7 gefunden wird.

Berni | Category: PHP
plotting masters - a professional guide - Teil II

Grafische Interpolation und Bestapproximation von numerischen Wertepaaren: Wir wollen Punkte auf einer Zeichenebene über verschiedene Verfahren miteinander verbinden.

EVAMasters | Category: PHP