I output a valid gif, but I only see its content, what should I do?

Question

I had an "older" server, now I upgraded to newest. I have something like this: img src="s.php", the s.php creates a GIF output. When I directly call this script, I only see the content of the image, instead of the actual picture. I saved the picture, it has no bug.

Answer 1

Use

ob_start();  
header('Content-Type: image/gif');  
echo //your image
ob_end_flush();

Answer 2

Add this before any output

header("Content-Type: image/gif");