add optional support for the X-Sendfile header

image.php

@@ -27,12 +27,22 @@
 		$filename = CACHE_DIR . '/images/' . $hash . '.png';
 
 		if (file_exists($filename)) {
-			header("Content-type: image/png");
-			$stamp = gmdate("D, d M Y H:i:s", filemtime($filename)). " GMT";
-			header("Last-Modified: $stamp", true);
-
-			readfile($filename);
-
+			/* See if we can use X-Sendfile */
+			$xsendfile = false;
+			if (function_exists('apache_get_modules') &&
+			    array_search('mod_xsendfile', apache_get_modules()))
+				$xsendfile = true;
+
+			if ($xsendfile) {
+				header("X-Sendfile: $filename");
+				header("Content-type: application/octet-stream");
+				header('Content-Disposition: attachment; filename="' . basename($filename) . '"');
+			} else {
+				header("Content-type: image/png");
+				$stamp = gmdate("D, d M Y H:i:s", filemtime($filename)). " GMT";
+				header("Last-Modified: $stamp", true);
+				readfile($filename);
+			}
 		} else {
 			header($_SERVER["SERVER_PROTOCOL"]." 404 Not Found");
 			echo "File not found.";