php计算经纬算法

		//经纬度算法
		$pi80 = M_PI / 180;
		$lat1=34.7465763;
		$lng1=113.65778739999996; 
		$lat2=34.684795; 
		$lng2=112.43594499999995; 
		$lat1 *= $pi80;  
		$lng1 *= $pi80;  
		$lat2 *= $pi80;  
		$lng2 *= $pi80;  
		$r = 6372.797; 
		// mean radius of Earth in km  
		$dlat = $lat2 - $lat1;  
		$dlng = $lng2 - $lng1;  
		$a = sin($dlat/2)*sin($dlat/2)+cos($lat1)*cos($lat2)*sin($dlng/2)*sin($dlng/2);  
		$c = 2 * atan2(sqrt($a), sqrt(1 - $a));  
		$km =round( $r * $c,2);
		// return ($miles ? ($km * 0.621371192) : $km);  
		dump($km.'km');