- var_dump: documentation ( source)
- abs: documentation ( source)
- tan: documentation ( source)
- asinh: documentation ( source)
- deg2rad: documentation ( source)
<?php
$lat = 60;
$lon = 160;
$nLon = ($lon / 360) + 0.5;
$nLat = abs((asinh(tan(deg2rad($lat))) / M_PI / 2) - 0.5);
var_dump($nLon, $nLat);