PHP function for converting web mercator (X,Y coords) to WGS84

gistfile1.txt

//Convert Web Mercator to WGS84
function toGeographic($X, $Y){
    if (abs($X) < 180 && abs($Y) < 90){
        return array('lat'=>0,'lng'=>0);
    }

    if (abs($X) > 20037508.3427892 || abs($Y) > 20037508.3427892){
        return array('lat'=>0,'lng'=>0);
    }

    $num3 = ($X / 6378137.0) * 57.295779513082323;
    $num4 = floor(($num3 + 180.0) / 360.0);
    $num5 = $num3 - ($num4 * 360.0);
    $num6 = 1.5707963267948966 - (2.0 * atan(exp((-1.0 * $Y) / 6378137.0)));
    
    //Return array(lat,lng);
    return ['lat'=>$num6 * 57.295779513082323, 'lng'=>$num5];
}