If you're using PHP < 5.5 you can use this code to add the same functionality. If you pass the wrong $mode in it will silently fail. You might want to add your own error handling for this case.<?phpif (!function_exists('imageflip')) { define('IMG_FLIP_HORIZONTAL', 0); define('IMG_FLIP_VERTICAL', 1); define('IMG_FLIP_BOTH', 2); function imageflip($image, $mode) { switch ($mode) { case IMG_FLIP_HORIZONTAL: { $max_x = imagesx($image) - 1; $half_x = $max_x / 2; $sy = imagesy($image); $temp_image = imageistruecolor($image)? imagecreatetruecolor(1, $sy): imagecreate(1, $sy); for ($x = 0; $x < $half_x; ++$x) { imagecopy($temp_image, $image, 0, 0, $x, 0, 1, $sy); imagecopy($image, $image, $x, 0, $max_x - $x, 0, 1, $sy); imagecopy($image, $temp_image, $max_x - $x, 0, 0, 0, 1, $sy); } break; } case IMG_FLIP_VERTICAL: { $sx = imagesx($image); $max_y = imagesy($image) - 1; $half_y = $max_y / 2; $temp_image = imageistruecolor($image)? imagecreatetruecolor($sx, 1): imagecreate($sx, 1); for ($y = 0; $y < $half_y; ++$y) { imagecopy($temp_image, $image, 0, 0, 0, $y, $sx, 1); imagecopy($image, $image, 0, $y, 0, $max_y - $y, $sx, 1); imagecopy($image, $temp_image, 0, $max_y - $y, 0, 0, $sx, 1); } break; } case IMG_FLIP_BOTH: { $sx = imagesx($image); $sy = imagesy($image); $temp_image = imagerotate($image, 180, 0); imagecopy($image, $temp_image, 0, 0, 0, 0, $sx, $sy); break; } default: { return; } } imagedestroy($temp_image); }}?>