Function handling
PHP Manual

function_exists

(PHP 4, PHP 5)

function_exists — Return TRUE if the given function has been defined

Descrierea

bool function_exists ( string $function_name )

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

Parametri

function_name

The function name, as a string.

Valorile întroarse

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

Notă: This function will return FALSE for constructs, such as include_once() and echo().

Exemple

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";
}
?>

Note

Notă: 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).

Vedeţi de asemenea


Function handling
PHP Manual