Get properties, ordered by the distance from an existing property. Latitude and longitude are stored in the address relationship.

Property.php

<?php

// Property::query()->nearest($property)->limit(5)->get();
// $property->nearest()->limit(5)->get();

public function scopeNearest(Builder $query, ?Property $property = null): Builder
{
    $property = $property ?? $this;
    $earthRadius = 3959;
    $latitude = $property->address->lat;
    $longitude = $property->address->lng;
    $distanceColumn = 'distance';

    $addressTable = $property->address->getTable();
    $addressKeyColumn = $property->address->getQualifiedKeyName();
    $addressRelationColumn = $property->qualifyColumn('address_id');
    $latitudeColumn = $property->address->qualifyColumn('lat');
    $longitudeColumn = $property->address->qualifyColumn('lng');

    $selects = [
        $property->qualifyColumn('*'),
        "(
            {$earthRadius} * Acos(
                Cos(Radians({$latitude})) *
                Cos(Radians({$latitudeColumn})) *
                Cos(Radians({$longitudeColumn}) -
                Radians({$longitude})) +
                Sin(Radians({$latitude})) *
                Sin(Radians({$latitudeColumn}))
            )
        ) AS `{$distanceColumn}`",
    ];

    return $query
        ->selectRaw(implode(', ', $selects))
        ->whereNot($property->getQualifiedKeyName(), $property->getKey())
        ->join($addressTable, $addressKeyColumn, '=', $addressRelationColumn)
        ->orderby($distanceColumn);
}