note 76025 added to function.set-error-handler

The manual states: "errcontext will contain an array of every variable that existed in the scope the error was triggered in. User error handler must not modify error context." But do you know WHY you must not modify the error context? It appears that errcontext is (in effect if not literally) created by taking $GLOBALS and adding the non-global local variables as additional entries in that array, then passing the whole thing *by reference*. (You can prove this to be true if you set up a custom error handler and then print_r($errcontext) within it, because $GLOBALS will be printed as a recursive array). In other words, the language in the manual is misleading, because errcontext is NOT a copy of the variables that existed when the error WAS triggered, but rather is a reference to the *existing LIVE variables* in the calling script. This includes superglobal variables like $_SERVER, $_POST, $_GET, etc., as well as all user-defined variables in scope. The significance of that is that if you modify errcontext, you will be modifying those other variables, not just for the life of your error handling function, but for the life of the calling script as well. That doesn't matter if you plan to halt execution in your error handling function, but it will lead to unexpected behavior if you modify $errcontext and then return to the program's normal flow after handling the error, because the variables will stay modified. For example, if you unset $_SERVER in your custom error handling function, it will remain unset once the function is over and you have returned to the page that generated the error. This should be made clearer in the manual, starting by marking errhandler with an ampersand (&) for passage by reference in the "Parameters" section above, like so: handler ( int $errno, string $errstr [, string $errfile [, int $errline [, array &$errcontext]]] ) ---- Server IP: 208.69.120.35 Probable Submitter: 68.163.129.98 ---- Manual Page -- http://www.php.net/manual/en/function.set-error-handler.php Edit -- https://master.php.net/note/edit/76025 Del: integrated -- https://master.php.net/note/delete/76025/integrated Del: useless -- https://master.php.net/note/delete/76025/useless Del: bad code -- https://master.php.net/note/delete/76025/bad+code Del: spam -- https://master.php.net/note/delete/76025/spam Del: non-english -- https://master.php.net/note/delete/76025/non-english Del: in docs -- https://master.php.net/note/delete/76025/in+docs Del: other reasons-- https://master.php.net/note/delete/76025 Reject -- https://master.php.net/note/reject/76025 Search -- https://master.php.net/manage/user-notes.php