note 130013 added to function.isset

isset() is not actually a function. It is a keyword. I'm surprised no one has pointed out this very important distinction. Keywords are implemented inline into the PHP Zend core processing engine. Functions are not. As a result, keywords generally have significant performance benefits over function calls, including most standard extension functions. Various efforts have been made for very specific functions over the years like array_key_exists() to get them closer to keyword level performance, but those are done on a case-by-case basis and are exclusively in the "ext/standard" extension that gets compiled into every PHP build. Most functions do not get such benefits and have to go through the comparatively heavyweight PHP function call logic. ---- Server IP: 45.112.84.4 Probable Submitter: 45.112.84.18 (proxied: 174.18.63.86) ---- Manual Page -- https://php.net/manual/en/function.isset.php Edit -- https://main.php.net/note/edit/130013 Del: integrated -- https://main.php.net/note/delete/130013/integrated Del: useless -- https://main.php.net/note/delete/130013/useless Del: bad code -- https://main.php.net/note/delete/130013/bad+code Del: spam -- https://main.php.net/note/delete/130013/spam Del: non-english -- https://main.php.net/note/delete/130013/non-english Del: in docs -- https://main.php.net/note/delete/130013/in+docs Del: other reasons-- https://main.php.net/note/delete/130013 Reject -- https://main.php.net/note/reject/130013 Search -- https://main.php.net/manage/user-notes.php