Resize an image from an url and return the new picture

resize.php

<?php

ob_start("ob_gzhandler");

function loadImage ($file) {
    $data = getimagesize($file);
        die(var_export($data));
    switch($data["mime"]){
        case "image/jpeg":
            $im = imagecreatefromjpeg($file);
            break;
        case "image/png":
            $im = imagecreatefrompng($file);
            break;
        default:
            throw new Exception('Img Type not managed');
    }
    return $im;
}

if (!isset($_GET['url']) || (!isset($_GET['w']) && !isset($_GET['h']))) {
    die('USAGE: resize.php?url=&lt;imageURL&gt;[&w=&lt;maxwidth&gt;][&h=&lt;maxheight&gt;]');
}

$url = $_GET['url'];

try {
    $image = loadImage($url);
} catch(Exception $e) {
    die('Unable to load this image');
}

$w = imagesx($image);
$h = imagesy($image);

//calculate new image dimensions (preserve aspect)
if (isset($_GET['w']) && !isset($_GET['h'])) {
    $new_w = intval($_GET['w']);
    $new_h = $new_w * ($h/$w);
} else if (!isset($_GET['w']) && isset($_GET['h'])) {
    $new_h = intval($_GET['h']);
    $new_w = $new_h * ($w/$h);
} else {
    $new_h = intval($_GET['h']);
    $new_w = intval($_GET['w']);

    if ($new_w * ($h/$w) > $new_h) {
        $new_w = $new_h * ($w/$h);
    } else if ($new_h * ($w/$h) > $new_w) {
        $new_h = $new_w * ($h/w);
    }
}

$im2 = ImageCreateTrueColor($new_w, $new_h);
imagecopyResampled ($im2, $image, 0, 0, 0, 0, $new_w, $new_h, $w, $h);

header('Content-type: image/png');
header("Content-Disposition: inline; filename=".basename($url).".png");
header('Last-Modified: ' . gmdate('D, d M Y H:i:s', filemtime($url)) . ' GMT');
header("Cache-Control: public");
header("Pragma: public");
imagepng($im2);
imagedestroy($im2);
imagedestroy($image);