Re: distinguish between null variable and unset variable

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; } -- Thanks! -Shawn http://www.spidean.com