Watermark youtube thumbnail using php - php

Question

I tried to overlay some text on a youtube thumbnail using php GD, but that does'nt seem to work.
The code I have tried is:
<?php
$im = file_get_contents('http://i.ytimg.com/vi/6E9wBFl5o-c/mqdefault.jpg');
$image = imagecreatefromjpeg($im);
$font_size = 14;
$color = imagecolorallocate($image, 255,255,255);
$black = imagecolorallocate($image, 0,0,0);
// and now we do the overlay - the layers of text start top to bottom, so
// the drop shadow comes first
// $image - the base image file we specified above
// $font_size - Well duh. Its the size of the font
// 0 - the angle of the text - we don't want an angle, so we leave it at 0
// 56 - pixels to the right from the leftmost part of the image
// 36 - pixels down from the top of the image
// $black - the color we defined above
// "Test Text" - the text we're overlaying - you can also use a variable here
ImageTTFText ($image, $font_size, 0, 56, 36, $black, "font.ttf","Test Text");
// Now add the actual white text "on top"
ImageTTFText ($image, $font_size, 0, 55, 35, $color, "font.ttf","Test Text");
header("Content-type: image/jpeg");
imagejpeg($image);
imagedestroy($image);
So how can I get the image returned with text written on it.

Answer 1

imagecreatefromjpeg needs a filename as parameter, see http://php.net/manual/function.imagecreatefromjpeg.php
this should work:
$image = imagecreatefromjpeg('http://i.ytimg.com/vi/6E9wBFl5o-c/mqdefault.jpg');

Answer 2

To debug the script you can access the url in the browser. Any warnings or error messages will be readible.
A simple error is that you declare a JPG file in the header, but return a PNG file.
header("Content-type: image/jpg");
imagepng($image);
Also make sure that the font file is really accessible from the PHP file.