Whenever you need to get nearest posts from lat and long and if you are working on laravel query builder. then you can get distance easily using DB::raw(), so you can learn from following example how to get nearest value from mysql laravel.
$lat = 1;
$lon = 1;
,DB::raw("6371 * acos(cos(radians(" . $lat . "))
* cos(radians(posts.lon) - radians(" . $lon . "))
+ sin(radians(" .$lat. "))
* sin(radians(posts.lat))) AS distance"))