PHP Mercator Projection

latlng2xy.php

<?php
//based on http://www.cnblogs.com/enjoyeclipse/archive/2013/01/18/2865700.html
function latlng2xy($lat, $lng, $zoom){
	if (abs($lat) > 85.0511287798066){
		return false;
	}
	$sin_phi = sin($lat * M_PI / 180);
	$norm_x = $lng / 180;
	$norm_y = (0.5 * log((1 + $sin_phi) / (1 - $sin_phi))) / M_PI;
	$tileRow = pow(2, $zoom) * ((1 - $norm_y) / 2);
	$tileColumn = pow(2, $zoom) * (($norm_x + 1) / 2);

	return array(
		'y'=>$tileRow,
		'x'=>$tileColumn
	);
}