function_usable()

function_usable($function_name)

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

This function runs a function_exists() check and if the Suhosin extension <http://www.hardened-php.net/suhosin/> is loaded, checks if it doesn’t disable the function being checked.

It is useful if you want to check for the availability of functions such as eval() and exec(), which are dangerous and might be disabled on servers with highly restrictive security policies.