function_exists
(PHP 3>= 3.0.7, PHP 4 )
function_exists --
Return
TRUE if the given function has been defined
Description
bool
function_exists ( string function_name)
Checks the list of defined functions, both built-in (internal) and
user-defined, for function_name. Returnerar TRUE vid framgång eller FALSE vid fel.
Note that 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).
Also note that
function_exists() will return
FALSE for constructs, such as
include_once()
and
echo().
See also method_exists() and
get_defined_functions().