PHP generate and display image thumbnail
===

I have found and modified a small php script for generating thumbnails

    $src = (isset($_GET['file']) ? $_GET['file'] : "");
    $width = (isset($_GET['maxwidth']) ? $_GET['maxwidth'] : 73);
    $thname = "xxx";
    
    $file_extension = substr($src, strrpos($src, '.')+1);
    		
    switch(strtolower($file_extension)) {
    	 case "gif": $content_type="image/gif"; break;
    	 case "png": $content_type="image/png"; break;
    	 case "bmp": $content_type="image/bmp"; break;
    	 case "jpeg":
    	 case "jpg": $content_type="image/jpg"; break;
    	 
    	 default: $content_type="image/png"; break;
     
    }
    		
    if (list($width_orig, $height_orig, $type, $attr) = @getimagesize($src)) {
    	$height = ($width / $width_orig) * $height_orig;
    }
    
    $tn = imagecreatetruecolor($width, $height) ;
    $image = imagecreatefromjpeg($src) ;
    imagecopyresampled($tn, $image, 0, 0, 0, 0, $width, $height, $width_orig, $height_orig);
    
    imagejpeg($tn, './media/'.$thname.'.'.$file_extension, 90);

It generates and saves thumbnails perfectly.

How can I display those thumbnails on the fly?

I tryed to add this at the bottom of a script

    header('Content-type: image/jpeg');
    $p = 'media/'.$thname.'.'.$file_extension;
    $a = file_get_contents($p);
    echo $a;
but it says `The image cannot be displayed because it contains errors`. What am I doing wrong?