PHP - Draw an image in memory

<?php
  // PHP - Draw an image in memory
  // reference: http://www.php.net/manual/en/ref.image.php
  $im = imagecreate($width, $height);

  // make some colours
  $white = imagecolorallocate($im, 255, 255, 255);
  $black = imagecolorallocate($im, 0, 0, 0);

  // set a background
  imagefill($im, 0, 0, $white);

  $text = 'Something';
  $font_number = 2; // try 2 to start with
  imagestring($im, $font_number, $x, $y, $text, $black);

  // we need somewhere to put the image
  $path = '/public_html/temp/'; // a server path to a temporary directory
  // make a unique number to ensure the image is not cached
  $unique = time();
  $url = $path.$unique.'gif';
  // save the image to the server
  $result = imagegif($im, $url);

  // get the http address for the image
  $url = get_site_url().'/temp/'.$unique.'.gif';
  echo '<img src="'.$url.'" />';

  // release the memory
  imagedestroy($im);

  // NB the temp directory will fill up over time