num_rows一直返回null

Question

我真的不明白为什么这不起作用。我已经检查了几次，甚至将其与我已经完成的其他例子进行比较。请注意，我已将它放到最简单的表单中，因此没有sql注入保护。那会晚一点。在这样的查询

$sql= "SELECT * FROM Users WHERE `email` = '$username' AND `password` = '$password'"; 

Answer 1

使用反引号列的应该是：

//since user and password is not blank, find user info using the email and password entered by user 
$sql= "SELECT * FROM `Users` WHERE `email` = '{$username}' AND `password` = '{$password}';"; 

Answer 2

您的查询

//user real escape string to prevent SQL injection 
$username = $_POST['username']; 
$password = $_POST['password']; 

//check if username and password is blank 
if (!$username || !$password) 
    die ("Not all the fields were filled in"); 

//Server details 
$host = 'localhost'; 
$user = 'tm_user'; 
$password = 'password'; 

//The database name 
$database = 'TransportMe'; 

// Create connection 
$con = new mysqli($host, $user, $password, $database); 

// Check connection 
if ($con->connect_error) { 
    die("Connection failed: " . $conn->connect_error); 
} 

//since user and password is not blank, find user info using the email and password entered by user 
$sql= "SELECT * FROM Users WHERE 'email'='$username' AND 'password' = '$password';"; 

//Get the results 
$result = $con->query($sql); 

//Check if null 
if ($result->num_rows == null) 
    die("Null");