fixed stream spit | tested on home-server, works fine.

b.php

@@ -4,17 +4,18 @@ $dir = "banners/";
 $files = scandir($dir);
 $images = array_diff($files, array('.', '..'));
 $name = $images[array_rand($images)];
-// open the file in a binary mode
-$fp = fopen($dir . $name, 'rb');
+
+// snags the extension
+$img_extension = pathinfo($name, PATHINFO_EXTENSION);
 
 // send the right headers
 header('Cache-Control: no-cache, no-store, must-revalidate'); // HTTP 1.1
 header('Pragma: no-cache'); // HTTP 1.0
 header('Expires: 0'); // Proxies
-header('Content-Type: ' . $fp['type']);
-header('Content-Length: ' . $fp['bytes']);
+header("Content-type: " . $img_extension);
+header("Content-Disposition: inline; filename=" . $name);
 
-// dump the picture and stop the script
-fpassthru($fp);
+// readfile displays the image, passthru seems to spits stream.
+readfile($dir.$name);
 exit;
 ?>