Checks the list of defined functions, both built-in
(internal) and user-defined, for
function_name. 成功回傳TRUE失敗回傳FALSE。
if (function_exists('imap_open')) { echo "IMAP functions are available. br \n"; } else { echo "IMAP functions are not available. br \n"; } |
See also method_exists() and
get_defined_functions().