PHP class to calculate south-west and north-east bounds given a longitude, latitude and distance edit

Geo::bounds

<?php
/**
 * @author Melvin Tercan
 * @link http://twitter.com/melvinmt
 **/

class Geo{

	public static function bounds($mylat, $mylon, $dist = 100, $unit = 'km', $pyth_invert = true){
		
		if(!$pyth_invert){
			$dist = sqrt(pow($dist, 2) *2); // pythagoras
		}elseif($pyth_invert){
			$dist = sqrt($dist / 2); // inverted pythagoras
		}else{
			// $pyth_invert = NULL;
		}
		
		$earth_km_rad = 6371; // earth radius in km
		
		switch ($unit){
				
			case "m": // meters
				$earth_rad = $earth_km_rad * 1000;
			break;
			
			case "mi": // miles
				$earth_rad = $earth_km_rad * 0.621371192;
			break;
			
			case "yd": // yards
				$earth_rad = $earth_km_rad * 1093.6133;
			break;
				
			case "ft": // feet
				$earth_rad = $earth_km_rad * 3280.8399;
			break;
			
			case "in": // inches
				$earth_rad = $earth_km_rad * 39370.0787;
			break;
			
			default: // km
				$earth_rad = $earth_km_rad;
			break;
		}
		
		// southwest
		$sw = Geo::destination_point($mylat, $mylon, 225, $dist, $earth_rad);
		
		// northeast
		$ne = Geo::destination_point($mylat, $mylon, 45, $dist, $earth_rad);
		
		return array('lat' => array(
					'min' => $sw['lat'], 
					'max' => $ne['lat'], 
					),
			     'lon' => array(
					'min' => $sw['lon'], 
					'max' => $ne['lon'],
				        ),
			     'sw' => $sw,
			     'ne' => $ne,
			     'dist' => $dist
			);
	}
	

	public static function destination_point($lat1, $lon1, $deg, $dist, $earth_rad = 6371){
	
		$distance = $dist / $earth_rad;
		$deg = deg2rad($deg);
	
		$lat1 = deg2rad($lat1);
		$lon1 = deg2rad($lon1);
	
		$lat2 = asin( sin($lat1) * cos($dist) + cos($lat1) * sin($dist) * cos($deg) );
		$lon2 = $lon1 + atan2( sin($deg) * sin($dist) * cos($lat1), cos($dist) - sin($lat1) * sin($lat2));
		$lon2 = ( $lon2 + 3 * pi() ) % ( 2*pi() ) - pi();
	
		return array('lat' => rad2deg($lat2), 'lon' => rad2deg($lon2));
	} 

}

?>