index.php

<?php

$dsn = "mysql:host=db;dbname=docker_compose_pet_project;charset=utf8";

try{
    $conn = new \PDO($dsn, "dcpp", "dcpp");
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
} catch (PDOException $e) {
    var_dump($e->getMessage());
}

$stmt = $conn->query("SELECT * FROM users");

$tpl = <<<EOT
    <h3>{id}</h3>
    <p>customer id: <b>{customer_id}</b><br />
    age: <b>{age}</b><br />
    city: <b>{city}</b><br />
    email: <b>{email}</b><br />
    firstname: <b>{firstname}</b><br />
    lastname: <b>{lastname}</b></p>
EOT;


foreach ($stmt->fetchAll() as $k => $item) {
    echo preg_replace_callback("/{([^}]+)}/", function ($matches) use ($item)
    {
        if ($matches[1] == 'id') {
            return bin2hex($item[$matches[1]]);
        }

        return $item[$matches[1]];
    }, $tpl);
}