PHP - Dynamically resize an image without storing it

It is really a hassle to resize an image uploaded to be stored in different sizes, why not we resize it dynamically? Here I will show you how to generate an image with php for different sizes as we wish:

code:

<?php
$newwidth = $_GET["width"];
$newheight = $_GET["height"];
$image = $_GET["url"];
$ratio = ($_GET["ratio"] != "")? $_GET["ratio"] : "false";
$dst_x = ($_GET["dst_x"] != "")? intval($_GET["dst_x"]) : 0;
$dst_y = ($_GET["dst_y"] != "")? intval($_GET["dst_y"]) : 0;
$src_x = ($_GET["src_x"] != "")? intval($_GET["src_x"]) : 0;
$src_y = ($_GET["src_y"] != "")? intval($_GET["src_y"]) : 0;

$src = imagecreatefromjpeg($image);
list($width,$height)=getimagesize($image);
$newwidth = ($newwidth != "")? $newwidth : $width;
$newheight = ($newheight != "")? $newheight : $height;
if ($ratio == "true") {
$ratio_orig = $width/$height;
if ($newwidth/$newheight > $ratio_orig) {
 $newwidth = $newheight*$ratio_orig;
} else {
 $newheight = $newwidth/$ratio_orig;
}
}
$tmp=imagecreatetruecolor($newwidth,$newheight);
imagecopyresampled($tmp,$src,$dst_x,$dst_y,$src_x,$src_y,$newwidth,$newheight,$width,$height);
imagejpeg($tmp);
header("Content-type: image/jpeg");
?>

How to use it :
-Save above as image.php
-Use it like : image.php?url=http://t2.gstatic.com/images?q=tbn:ZqzO2ew7hmrDJM%3Ahttp://farm3.static.flickr.com/2204/2403693037_0b63bdc4b4.jpg&width=100&height=100&ratio=true