Naive postgis MVT tileserver

naive.php

<?php

require('../vendor/autoload.php');
$dotenv = Dotenv\Dotenv::createMutable(__DIR__ . '/../');
$dotenv->load();

const WORLD_MERCATOR_MAX = 20037508.3427892;
const WORLD_MERCATOR_MIN = -WORLD_MERCATOR_MAX;
const WORLD_MERCATOR_SIZE = WORLD_MERCATOR_MAX - WORLD_MERCATOR_MIN;

$uri = $_SERVER['REQUEST_URI'] ?? '';

if (preg_match('|/(?P<z>\d+)/(?P<x>\d+)/(?P<y>\d+)(\.pbf?)$|', $uri, $matches)) {

    $tile = [
        'x' => (int)$matches['x'],
        'y' => (int)$matches['y'],
        'z' => (int)$matches['z'],
    ];

    // Sanity checks
    if ($tile['x'] < 2 ** $tile['z'] && $tile['y'] < 2 ** $tile['z'] && $tile['x'] >= 0 && $tile['y'] >= 0) {

        // Make tile envelope
        $world_tile_size = 2 ** $tile['z'];
        $tile_mercator_size = WORLD_MERCATOR_SIZE / $world_tile_size;

        $envelope = [
            'xmin' => WORLD_MERCATOR_MIN + $tile_mercator_size * $tile['x'],
            'xmax' => WORLD_MERCATOR_MIN + $tile_mercator_size * ($tile['x'] + 1),
            'ymin' => WORLD_MERCATOR_MAX - $tile_mercator_size * ($tile['y'] + 1),
            'ymax' => WORLD_MERCATOR_MAX - $tile_mercator_size * $tile['y'],
        ];

        $envelope['segsize'] = ($envelope['xmax'] - $envelope['xmin']) / 4;

        // Build bounds SQL
        $bounds_sql = <<<SQL
        ST_Segmentize(ST_MakeEnvelope(
            {$envelope['xmin']}, 
            {$envelope['ymin']}, 
            {$envelope['xmax']}, 
            {$envelope['ymax']}, 
            3857), {$envelope['segsize']})
        SQL;

        $tile_sql = <<<SQL
        WITH bounds AS (SELECT {$bounds_sql} AS geom, {$bounds_sql}::box2d AS b2d),
             mvtgeom AS (
                SELECT ST_AsMVTGeom(ST_Transform(t.geom, 3857), bounds.b2d) AS geom, 
                       objectcode,
                       parcelcode,
                       coalesce(
                           (select full_name from aw_eka e where st_contains(t.geom, e.geom) limit 1),
                           (select full_name from aw_eka e, kkparcel p where p.code = t.parcelcode and st_contains(p.geom, e.geom) limit 1),
                           'Neizdevās noteikt adresi'
                       ) as address
                FROM kkbuilding t, bounds
                WHERE ST_Intersects(t.geom, ST_Transform(bounds.geom, 4326))
            ) 
            SELECT ST_AsMVT(mvtgeom.*) FROM mvtgeom
        SQL;

        $DB = new PDO($_ENV['DB_DSN'], $_ENV['DB_USER'], $_ENV['DB_PASSWORD']);
        $data = $DB->query($tile_sql)->fetchColumn();

        fpassthru($data);
    } else {
        http_response_code(400);
    }
} else {
    http_response_code(404);
}