Function handling Функции
PHP Manual

function_exists

(PHP 4, PHP 5)

function_existsReturn TRUE if the given function has been defined

Описание

bool function_exists ( string $function_name )

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

Параметри

function_name

The function name, as a string.

Връщани стойности

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

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

Примери

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";
}
?>

Бележки

Забележка: 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).

Вж. също


Function handling Функции
PHP Manual