note 92043 added to function.isset
| From: | DanielNorton at osu1 dot php dot net | Date: | Mon, 06 Jul 2009 21:43:23 +0000 |
| Subject: | note 92043 added to function.isset | ||
| Groups: | php.notes | ||
| Request: | Send a blank email to php-notes+get-157985@lists.php.net to get a copy of this message | ||
The code below shows how to distinguish between an undefined variable and a variable defined as
NULL. I'll keep this code maintained and annotated at http://www.danielnorton.com/nerd/code/php/isset
<?php
global $errhandler_ctr;
function errhandler($errno, $errstr, $errfile, $errline, $errcontext ) {
global $errhandler_ctr;
$errhandler_ctr = $errhandler_ctr ? $errhandler_ctr++ : 1;
return TRUE;
}
function _strval($arg) {
if ((!is_string($arg)) && is_bool($arg)) return $arg ? "TRUE" :
"FALSE";
return strval($arg);
}
$isnull=NULL; // defined as NULL
unset($undef); // not defined
$errhandler_ctr = 0;
$sv = set_error_handler("errhandler");
$is_defined = !is_null($isnull);
set_error_handler($sv);
if (!$errhandler_ctr) $is_defined = TRUE;
print $is_defined ? "TRUE\n" : "FALSE\n";
$errhandler_ctr = 0;
$sv = set_error_handler("errhandler");
$is_defined = !is_null($undef);
set_error_handler($sv);
if (!$errhandler_ctr) $is_defined = TRUE;
print $is_defined ? "TRUE\n" : "FALSE\n";
?>
Output:
TRUE
FALSE
----
Server IP: 69.147.83.197
Probable Submitter: 70.114.204.95
----
Manual Page -- http://www.php.net/manual/en/function.isset.php
Edit -- https://master.php.net/note/edit/92043
Del: integrated -- https://master.php.net/note/delete/92043/integrated
Del: useless -- https://master.php.net/note/delete/92043/useless
Del: bad code -- https://master.php.net/note/delete/92043/bad+code
Del: spam -- https://master.php.net/note/delete/92043/spam
Del: non-english -- https://master.php.net/note/delete/92043/non-english
Del: in docs -- https://master.php.net/note/delete/92043/in+docs
Del: other reasons-- https://master.php.net/note/delete/92043
Reject -- https://master.php.net/note/reject/92043
Search -- https://master.php.net/manage/user-notes.php