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().