PHP - function_exists

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Metóda - function_exists

(PHP 4, PHP 5, PHP 7)

Checks whether a specified function exists, including user-defined functions.

Note: Some functions can exist based on a result returned by this function, but could not be unusable due to compile-time or run-time configuration of the PHP interpreter. These can be e.g. image manipulation functions.

Procedurálne

• function function_exists (string $function_name) : bool

Parametre

Názov	Dátový typ	Predvolená hodnota	Popis
$function_name	string		The name of the function as string.

Mávratovej hodnoty

Vracia: bool

Returns true if the specified function exists and is a function.

Note: This function returns false for constructs which aren't functions, for example include_once or echo.

Príklady

<?php

echo function_exists('implode') ? 'Function exists.' : 'Function does not exist.'; // Output: 'Function exists.'
echo function_exists('echo')    ? 'Function exists.' : 'Function does not exist.'; // Output: 'Function does not exist.'

echo function_exists('nonexistentFunction') ? 'Function exists.' : 'Function does not exist.'; // Output: 'Function does not exist.'