(PHP 3 >= 3.0.7, PHP 4, PHP 5)
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. Returns TRUE on success or FALSE on failure.
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(),
is_callable() and
get_defined_functions().
