function_exists Return &true; if the given function has been defined boolfunction_exists stringfunction_name Checks the list of defined functions, both built-in (internal) and user-defined, for function_name. &return.success; \n"; } else { echo "IMAP functions are not available.
\n"; } ?> ]]> 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.