Description:
------------
imagecreatefromstring has an undocumented warning when creating from an invalid image source.

Test script:
---------------
<?php
var_dump(imagecreatefromstring('whee php'));

Expected result:
----------------
bool(false)

Actual result:
--------------
PHP Warning:  imagecreatefromstring(): Data is not in a recognized format in /test.php on line 2
PHP Stack trace:
PHP   1. {main}() /test.php:0
PHP   2. imagecreatefromstring() /test.php:2

Warning: imagecreatefromstring(): Data is not in a recognized format in /test.php on line 2

Call Stack:
    0.0001     224640   1. {main}() /test.php:0
    0.0001     225296   2. imagecreatefromstring() /test.php:2

bool(false)