php - 在非对象上调用成员函数 fetch()

Question

所以，我很确定我的查询应该没问题。但是我做了一个 var_dump 并且它确实返回 false，所以我不知道为什么。有人可以告诉我我的查询有什么问题或诸如此类的问题，以及如何解决吗？我很确定这不是我的自定义函数 db_​​connect，它以前工作过。可能是什么问题呢？

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();

Answer 1

您需要将 $email 变量放在引号内：

$result = $dbh->query("SELECT balance FROM users WHERE email = '$email'"); //get balance 
$result1 = $dbh->query("SELECT id FROM users WHERE email = '$email'");

或连接：

$result = $dbh->query("SELECT balance FROM users WHERE email = '".$email."'");
$result1 = $dbh->query("SELECT id FROM users WHERE email = '".$email."'");