php计算经纬算法

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//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');