PHP Lat Lng Distance and Bearing

<?php
$DEG2RAD = 3.14159265359 / 180;
$EARTHRAD = 6371000;
function distbear( $a, $b ){
    // distance and bearing at point $a to go to point $b
    global $EARTHRAD;
    global $DEG2RAD;
    $_a = pow( sin( 0.5 * ( $b->lat - $a->lat ) ), 2 ) +
        cos( $b->lat ) * cos( $a->lat ) * pow( sin( 0.5 * ( $b->lng - $a->lng ) ), 2 );
    $_d = $EARTHRAD * 2 * atan2( sqrt( $_a ), sqrt( 1 - $_a ) );
    $_n = cos( $a->lat ) * sin( $b->lat ) - sin( $a->lat ) * cos( $b->lat ) * cos( $b->lng - $a->lng ); //north
    $_e = sin( $b->lng - $a->lng ) * cos( $b->lat ); //east
    $_b = atan2( $_e, $_n ); // FORMULA: bear = atan2( 90deg=east, 0deg=north ) //south=-north, west=-east
    return (object) array( 'distance'=>$_d, 'bearing'=>$_b );
}
$a = (object) array('lat' => $DEG2RAD * +0.0000, 'lng' => $DEG2RAD * +0.0000 );
$b = (object) array('lat' => $DEG2RAD * +0.0000, 'lng' => $DEG2RAD * -1.0000 ); // west
$b = (object) array('lat' => $DEG2RAD * +0.0000, 'lng' => $DEG2RAD * +1.0000 ); // east
$b = (object) array('lat' => $DEG2RAD * +1.0000, 'lng' => $DEG2RAD * +0.0000 ); // north
$b = (object) array('lat' => $DEG2RAD * -1.0000, 'lng' => $DEG2RAD * +0.0000 ); // south
print_r( distbear( $a, $b ) );