mysqli_stmt :: bind_result（）：绑定变量数与预准备语句中的字段数不匹配

Question

I’ve been trying to code a login form in PHP using a prepared statement but every time I try to log in I get the following error:

mysqli_stmt::bind_result(): Number of bind variables doesn't match number of fields in prepared statement

Here is my code:

<?php
session_start();

$mysqli = new mysqli("localhost", "root" , "" , "security");
if(mysqli_connect_errno()){
    echo "Wrong" ;
}
if($stmt = $mysqli->prepare("SELECT username AND password FROM users WHERE username =? AND password =?")){
    $username = $_POST['name'];
    $password = $_POST['password'];
    $stmt->bind_param('ss' ,$username ,$password);
    $stmt->execute();
    $stmt->bind_result($password ,$username);
    if($stmt->fetch() == 'true')
    {
        echo "welcome";
    } else{
        echo "wrong password";
    }
}
?>

Can someone tell me why this is happening?

Answer 1

If that really is your code, it may be that either $_POST["name"] or $_POST["password"] is an array, so that bind_param binds more than just one value.

Check:

var_dump($_POST["name"]);
var_dump($_POST["password"]);