Re: distinguish between null variable and unset variable

Shawn McKenzie wrote: > Daniel Brown wrote: >> On Wed, Jan 21, 2009 at 20:27, Jack Bates <ms419@freezone.co.uk> wrote: >>> How can I tell the difference between a variable whose value is null and >>> a variable which is not set? >> Unfortunately, in PHP - like other languages - you can't. >> >> A variable is considered to be null if: >> * it has been assigned the constant NULL. >> * it has not been set to any value yet. >> * it has been unset(). >> > > I'm not in a position to test right now, but using Dan's logic I would > turn it around and test for isset first and then is_null. This makes > sense to me, but maybe it is flawed: > > if (isset($var) && is_null($var)) { > echo "$var is set and is null"; > } > > Or maybe a function to return is the $var === null: > > > function eq_null(&$var) > { > return (isset($var) && is_null($var)) ? true : false; > } > Or something like this (dunno, just brainstorming): function setornull(&$var) { if (!isset($var)) { return false; } elseif (is_null($var)) { return null; } return true; } -- Thanks! -Shawn http://www.spidean.com