Thumbnail creation function

<?php
   /*
    * Function that reads a directory and creates thumbs
   */

   function createThumbs( $pathToImages, $pathToThumbs, $thumbWidth ){
      // open the directory
      $dir = opendir( $pathToImages );

      // loop through it, looking for any/all JPG files:
      while (false !== ($fname = readdir( $dir ))) {
       // parse path for the extension
       $info = pathinfo($pathToImages . $fname);
       // continue only if this is a JPEG image
       if ( strtolower($info['extension']) == 'jpg' ){
          echo "Creating thumbnail for {$fname} <br />";

          // load image and get image size
          $img = imagecreatefromjpeg( "{$pathToImages}{$fname}" );
          $width = imagesx( $img );
          $height = imagesy( $img );

          // calculate thumbnail size
          $new_width = $thumbWidth;
          $new_height = floor( $height * ( $thumbWidth / $width ) );

          // create a new temporary image
          $tmp_img = imagecreatetruecolor( $new_width, $new_height );

          // copy and resize old image into new image
          imagecopyresized( $tmp_img, $img, 0, 0, 0, 0, $new_width, $new_height, $width, $height );

          // save thumbnail into a file
          imagejpeg( $tmp_img, "{$pathToThumbs}{$fname}" );
      }
  }
  // close the directory
  closedir( $dir );
}

// Usage:
createThumbs("upload/","upload/thumbs/",100);
?>