<?php 
function flip_image($imgPath)
{
  // flip from left to right (mirror image)
  $src = imagecreatefromjpeg($imgPath);
  $width = imagesx($src);
  $height = imagesy($src);
  $dst = imagecreate($width, $height);

  for($x = 0; $x < $width; $x++) {
    imagecopy($dst, $src, ($width-1) - $x, 0, $x, 0, 1, $height);
  }

  imagedestroy($src);
  unlink($imgPath);   // need to unlink before writing due to perms issue
  imagejpeg($dst, $imgPath);
  imagedestroy($dst);
  return;
}
?>