Geospatial sort by distance using Laravel and MySQL. I'm using a point column named geolocation in a table called things.

GeoSpatialThingController.php

<?php

class GeoSpatialThingController extends \BaseController {
	
	/**
	 * Display a listing of the resource.
	 *
	 * @return Response
	 */
	public function index()
	{
		// Using fairly new ST_Distance and ST_Within function in MySQL
		// 60 nautical miles is approx 69 miles
		
		$lat = 6.0;
		$lon = 52.0;
		$maximumDistance = 1000; // Distance in Miles
		$lonBound1 = $lon - $maximumDistance / abs(cos(deg2rad($lat)) * 69);
		$lonBound2 = $lon + $maximumDistance / abs(cos(deg2rad($lat)) * 69);
		$latBound1 = $lat - ($maximumDistance / 69);
		$latBound2 = $lat + ($maximumDistance / 69);

		$things = Thing::whereRaw("
		ST_Within(
			geolocation,
			envelope(
				linestring(
					point($lonBound1, $latBound1),
					point($lonBound2, $latBound2)
				)
			)
		)")->orderByRaw("
		ST_Distance(
			geolocation,
			GeomFromText('POINT($lat $lon)')
		)")->get();

		return $things;

	}
}

migration.php

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;

class CreateTable extends Migration {

	/**
	 * Run the migrations.
	 *
	 * @return void
	 */
	public function up()
	{
		Schema::create('things', function(Blueprint $table) {
    			$table->increments('id');
			$table->timestamps();
		});
		DB::statement("ALTER TABLE things ADD COLUMN geolocation POINT"); 
	}

	/**
	 * Reverse the migrations.
	 *
	 * @return void
	 */
	public function down()
	{
		Schema::drop('things');
	}

}

Can you explain about the "max-distance" variable? in "miles" ?