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PHP

Return TRUE if the given function has been defined


function_exists

(PHP 4, PHP 5)

function_existsReturn 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



Content

Android Reference

Java basics

Java Enterprise Edition (EE)

Java Standard Edition (SE)

SQL

HTML

PHP

CSS

Java Script

MYSQL

JQUERY

VBS

REGEX

C

C++

C#

Design patterns

RFC (standard status)

RFC (proposed standard status)

RFC (draft standard status)

RFC (informational status)

RFC (experimental status)

RFC (best current practice status)

RFC (historic status)

RFC (unknown status)

IT dictionary

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