Mysql致命错误：未捕获的错误：在布尔值上调用成员函数fetch（）

Question

<?php$host = "localhost";$user = "root";$password = '';$dbname = "rokon";$dsn = 'mysql:host='.$host.';dbname'.$dbname;$pdo = new PDO($dsn, $user, $password);$query = 'SELECT * FROM customar';$query = $pdo->query($query);while($row = $query->fetch(PDO::FETCH_OBJ)){    echo $row->firstname;    echo '<br>';}?>运行此代码时出现错误，错误是致命错误：未被捕获的错误：在布尔值上调用成员函数fetch（）