PHP imagecolorclosest() function

<?php
   $img = imagecreatefrompng(
   'https://www.tutorialspoint.com/assets/videos/courses/19/images/course_19_image.png');
   imagetruecolortopalette($img, false, 255);
   $val = imagecolorclosest($img, 20, 90, 140);
   $val = imagecolorsforindex($img, $val);
   $val = "({$val['red']}, {$val['green']}, {$val['blue']})";
   echo "Closest = " . $val;
   imagedestroy($img);
?>