Thank you for this bug report. To properly diagnose the problem, we
need a short but complete example script to be able to reproduce
this bug ourselves. 

A proper reproducing script starts with <?php and ends with ?>,
is max. 10-20 lines long and does not require any external 
resources such as databases, etc. If the script requires a 
database to demonstrate the issue, please make sure it creates 
all necessary tables, stored procedures etc.

Please avoid embedding huge scripts into the report.

Sample Code: taken out pf PHP Doumentation. It's an example by php documentation to illustrate the use of imagecreate().

<?php
header("Content-type: image/png");
$im = @imagecreate(110, 20)
    or die("Cannot Initialize new GD image stream");
$background_color = imagecolorallocate($im, 0, 0, 0);
$text_color = imagecolorallocate($im, 233, 14, 91);
imagestring($im, 1, 5, 5,  "A Simple Text String", $text_color);
imagepng($im);
imagedestroy($im);
?>

remove the "?>" and everything will run fine.

You are sending chars (like new lines and white spaces).

It didn't work by removing the end "?>". 

Problem was due to script encoding. I was using 'Notepad++' which has been set 'utf-8'. When I changed the encoding to 'ANSI' everything worked EVEN with the end "?>"