php creating image cant include file?

Question

<?php
header('Content-Type: image/png');
$im = @imagecreate(100, 100);
$color = imagecolorallocate($im, 10,10,10);
imagefill($im, 50, 50, $color);
imagePNG($im);
imagedestroy($im);
?>

this code works but if I put there require_once

require_once('file.php');

it doesn't work why?

Answer 1

I had some problem yesterday. I resolved erasing all spaces from all rows of included file. Last row without CR/LF I hope this is useful

Answer 2

created a page "file.php" that contain only just phpinfo() and call it via "require_once('file.php');"...

look like your png is not being treated as png and not being render or being destroy image here