WeberDev.com PHP and MySQL Code

LOG IN
BEGINNER GUIDES  |  PHP CLASSES  |  CODE SEARCH  |  ARTICLES SEARCH  |  PHP FORUMS  |  PHP MANUAL  |  PHP FUNCTIONS LIST  |  WEB SITE TEMPLATES
Start typing to search for PHP and MySQL Code Snippets and Articles Search
Submit a code Example / Snippet Submit Your Code
Search Engine Optimization Monitor SEO Monitor
Web Site UpTime Monitor UpTime Monitor
WeberDev's Monthly code contest PHP Code Contest
Your Personal Examples List My Favorite Examples
Your Personal Articles List My Favorite Articles
Edit Account Info Update Your Profile
More Weber Sites
PHP Code Search
Web Development Forums
Learn MySQL Playing Trivia
PHPBB2 Templates
Web Development Index
PHP Web Logs (BLogs)
Web Development Resources
Web Development Content
Recommended Links
PHPClasses
PHP Editor
PHP Jobs
Vision.To Design
Ajax Tutorials
PHP Programming Help
PHP/MySQL Programming
Webmaster Resources
Webmaster Forum
XML meta language
website builder
Recommended
Submit Site
Forex Trading Online forex trading platform
Return TRUE if the given function has been defined

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