<?php
// Load an image
$im = imagecreatefromgif('phplogo.gif');
// Get closest colors from the image
$colors = array();
$colors[] = imagecolorresolve($im, 255, 255, 255, 0);
$colors[] = imagecolorresolve($im, 0, 0, 200, 127);
// Output
print_r($colors);
imagedestroy($im);
?>
The above example will output something similar to:
Array ( [0] => 89 [1] => 85 )