Prints a list of the 40 moon pairs that are closest to each other.

moon_distance.php

<?php

$db = new PDO('sqlite:sqlite-latest.sqlite');

function sortDistances(MoonDistance $a, MoonDistance $b) {
    return $a->getDistance() - $b->getDistance();
};

$moons = $db->query('SELECT a.solarSystemID, a.x + b.x as x, a.y + b.y as y, a.z + b.z as z, a.itemName from mapDenormalize a left join mapSolarSystems b on (a.solarSystemID = b.solarSystemID) where a.typeID = 14');
$moonsBySolarSystem = [];
foreach ($moons as $moon) {
    $solarSystemID = $moon['solarSystemID'];
    if (!isset($moonsBySolarSystem[$solarSystemID])) {
        $moonsBySolarSystem[$solarSystemID] = [];
    }

    $moonsBySolarSystem[$solarSystemID][] = new Moon($moon);
}

$closestDistances = [];
foreach ($moonsBySolarSystem as $solarSystemID => $moons) {
    $moonCount = count($moons);

    if ($moonCount > 1) {
        $distances = [];
        for ($i = 0; $i < $moonCount; $i++) {
            $moonA = $moons[$i];

            for ($j = $i + 1; $j < $moonCount; $j++) {
                $distances[] = new MoonDistance($moonA, $moons[$j]);
            }
        }

        usort($distances, 'sortDistances');

        $closestDistances[] = $distances[0];
    }
}

usort($closestDistances, 'sortDistances');
echo "CLOSEST MOON DISTANCES:\n";
echo join("\n", array_slice($closestDistances, 0, 40));

class MoonDistance
{
    private $moonA;
    private $moonB;
    private $distance;

    public function __construct(Moon $moonA, Moon $moonB)
    {
        $this->moonA = $moonA;
        $this->moonB = $moonB;

        $this->distance = sqrt(
            pow($moonB->getX() - $moonA->getX(), 2) +
            pow($moonB->getY() - $moonA->getY(), 2) +
            pow($moonB->getZ() - $moonA->getZ(), 2)
        );
    }


    public function __toString()
    {
        return sprintf('%s, %s: %s km', $this->moonA, $this->moonB, number_format(floor($this->distance / 1000)));
    }

    public function getDistance()
    {
        return $this->distance;
    }
}

class Moon
{
    private $name;
    private $x;
    private $y;
    private $z;

    public function __construct($moonData)
    {
        $this->name = $moonData['itemName'];
        $this->x = $moonData['x'];
        $this->y = $moonData['y'];
        $this->z = $moonData['z'];
    }

    public function __toString()
    {
        return $this->name;
    }

    public function getX()
    {
        return $this->x;
    }

    public function getY()
    {
        return $this->y;
    }

    public function getZ()
    {
        return $this->z;
    }
}