empty($var) will return TRUE if $var is empty (according to the definition of 'empty' above) AND if $var is not set.

I know that the statement in the "Return Values" section of the manual already says this in reverse:

"Returns FALSE if var has a non-empty and non-zero value." 

but I was like "Why is this thing returning TRUE for unset variables???"... oh i see now... Its supposed to return TRUE for unset variables!!!

<?php
  ini_set('error_reporting',E_ALL);
  ini_set('display_errors','1');
  empty($var);
?>