<?php

declare(strict_types=1);

$mode = $argv[1] ?? '';
$sql = getenv('MDN_SQL') ?: '';
$params = [];
$paramCount = (int) (getenv('MDN_PARAM_COUNT') ?: 0);

for ($index = 0; $index < $paramCount; $index++) {
    $params[] = getenv('MDN_PARAM_'.$index);
}

$pdo = new PDO(
    'mysql:host='.getenv('MDN_DB_HOST').';dbname='.getenv('MDN_DB_NAME').';charset=utf8mb4',
    getenv('MDN_DB_USER'),
    getenv('MDN_DB_USER_PASS'),
    [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION],
);

$interpolatedSql = $sql;

foreach ($params as $value) {
    $quoted = $value === null ? 'NULL' : $pdo->quote((string) $value);
    $interpolatedSql = preg_replace('/\?/', $quoted, $interpolatedSql, 1);
}

$stmt = $pdo->query($interpolatedSql);

if ($mode === 'scalar') {
    $value = $stmt->fetchColumn();

    if ($value !== false) {
        echo $value;
    }
}