(PECL imagick 2.0.0)
Imagick::flopImage — Creates a horizontal mirror image
Creates a horizontal mirror image by reflecting the pixels around the central y-axis.
   Returns TRUE on success.
  
Throws ImagickException on error.
Example #1 Imagick::flopImage()
<?php
function flopImage($imagePath) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->flopImage();
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?>