Function handling Funkcje
PHP Manual

function_exists

(PHP 4, PHP 5)

function_existsReturn TRUE if the given function has been defined

Opis

bool function_exists ( string $function_name )

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

Parametry

function_name

The function name, as a string.

Zwracane wartości

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

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

Przykłady

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";
}
?>

Notatki

Informacja: 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).

Patrz także


Function handling Funkcje
PHP Manual