Description:
------------
Well, reading the manual about empty() you should think it checks whether the given variable is set before it checks whether it is empty. 
(Given example there: 
if (empty($var)) {
   echo '$var is either 0, empty, or not set at all';
})
However, when $var really is not set, i get a Memory Leak (in a big script). I reduced the script to the code below and now even get a Segmentation fault.

Reproduce code:
---------------
<?php
if(empty($foo)){
	echo 'empty';
}else{
	echo 'not empty';
}
?>

Expected result:
----------------
Echoing "empty" and nothing else.

Actual result:
--------------
Echoing "empty"
Valgrind says: http://tdc.medieval-wars.de/valgrind.txt.pid27963
Probably most important:
==27963== Process terminating with default action of signal 11 (SIGSEGV)
==27963==  Access not within mapped region at address 0xF45
==27963==    at 0x81EDD17: zend_execute_scripts (/home/necmon/php5-200501101930/Zend/zend.c:1059)
==27963==    by 0x819E50D: php_execute_script (/home/necmon/php5-200501101930/main/main.c:1636)
==27963==    by 0x8277DAE: main (/home/necmon/php5-200501101930/sapi/cli/php_cli.c:944)

(Note: this does NOT only happen with the cli version!)