Generate thumbnails on the fly

thumbnail.php

<?php
if (!isset($_GET['src'])) {
	//for testing, navigate to thumbnail.php?img=page/to/yourimage.jpg
	echo "<img src='/thumbnail.php?src={$_GET['img']}' />";
} else {
	header ("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); 
	header ("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); 
	header ("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1 
	header ("Pragma: no-cache"); // HTTP/1.0
	header("Content-type: image/pjpeg");
	header("Cache-Control: private");
	header("Content-Description: PHP Generated Data");
	
	//get the size of the image
	//$_GET['src'] can be a URL or a path
	list($width, $height) = getimagesize($_GET['src']);
	
	//if specifying a height, set it
	$newheight = isset($_GET['h']) ? $_GET['h'] : 66;
	
	//calculate the proportional width, if height is set
	$newwidth = isset($_GET['h']) ? ($width * ($newheight / $height)) : 96;
	
	$thumb = imagecreatetruecolor($newwidth, $newheight);
	$source = imagecreatefromjpeg($_GET['src']);
	imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
	
	//this echoes out the jpg
	imagejpeg($thumb);
}

Is this crazy?

Perhaps because you are generating it every time? You could save it, check if the source image has changed then create a new one. This would only be a problem if you were getting hit a whole pile. Also, you might find that you will run out of memory if you load a massive image.

header("Content-type: image/pjpeg"); => header("Content-type: image/jpeg");