对非对象的成员函数fetch(）的调用

所以，我确信我的查询应该是好的。但我做了一个var_dump，它确实返回false，所以我不知道为什么。有人能告诉我我的查询出了什么问题吗？以及如何修复它？我确信这不是我的自定义函数db_connect，它以前工作过。可能是什么问题？

这是我的代码：

require_once("includes/helpers.php");
session_start();
$dbh = connect_db('mysql:host=localhost;dbname=project1', 'jharvard', 'crimson');
if (!isset($_POST['quantity'])) { //go back if incomplete
    redirect('search');
}   
if (!isset($_SESSION['email'])) {
    redirect('index');
}
elseif (!isset($_SESSION['row'])) {
    redirect('stocks');
}
$amount = htmlspecialchars($_POST['quantity']);
$value = htmlspecialchars($_SESSION['row']);
$email = htmlspecialchars($_SESSION['email']);
$name = htmlspecialchars($_SESSION['q']);   
if (!filter_var($amount, FILTER_VALIDATE_INT) || $amount < 0) {
    redirect('search');
}
$dbh->beginTransaction();
$result = $dbh->query("SELECT balance FROM users WHERE email = $email"); //get balance 
$result1 = $dbh->query("SELECT id FROM users WHERE email = $email"); //get id
var_dump($result);
$bal = $result->fetchAll(PDO::FETCH_NUM);
$id = $result1->fetch(PDO::FETCH_ASSOC);

//if ($bal < $amount * $value) {
//  redirect ('search');
//} 
$bal = $bal - $amount * $value; //subtracting from total
$dbh->exec("INSERT INTO stocks (name, shares, id) VALUES ('$name', '$amount', '$id')");
$dbh->commit();