Question

It seems like my code works to check for null if I do

if ($tx)  

or

if (isset($tx)) 

why would I do the second one when it’s harder to write?

Answer 1

I want to point out that everyone’s reponse I’ve read here should have one caveat added:

‘isset() will return FALSE if testing a variable that has been set to NULL’ (php.net/isset).

This means that in some cases, like checking for a GET or POST parameter, using isset() is enough to tell if the variable is set (because it will either be a string, or it won’t be set). However, in cases where NULL is a possible value for a variable, which is fairly common when you get into objects and more complex applications, isset() leaves you high and dry.

For example (tested with PHP 5.2.6 with Suhosin-Patch 0.9.6.2 (cli) (built: Aug 17 2008 09:05:31)):

<?php $a = ''; $b = NULL; var_dump(isset($a)); var_dump(isset($b)); var_dump(isset($c)); 

outputs:

bool(true) bool(false) bool(false) 

Thanks, PHP!