无法使用“ execute（）”执行我的PDO查询，并得到“ bindParam（）”错误

Question

I'm creating a PDO Login class to use on my projects, but since I'm new to it I'm not being able to bind parameters to a prepared sql statement. Here's the function that is ment to do it :

include_once('connection.php');

class User{

    protected $db;

    public function __construct(){
        $oConnection = new Connection;
        $this->db = $oConnection->getConnection();
        //var_dump($this->db);
    }

    public function Login($name, $pass){
        if(!empty($name) && !empty($pass)){         
            $st = $this->db;
            $st->prepare("SELECT * FROM users WHERE user_name=? and user_password=?");
            $st->bindParam(1, $name);
            $st->bindParam(2, $pass);
            $st->execute();
            var_dump($st);

            if($st->rowCount == 1){
                echo "User verified, Acces granted.";
            }else{
                echo "Incorrect username or password.";
            }

        }else{
            echo "Please fill in the entire form";
        }
    }

}

And here is the Connection :

class Connection{

    protected $db;

    //Construct
    public function Connection(){

    $conn = NULL;
        try{
            $conn = new PDO("mysql:host=localhost;dbname=<db_name>", "<db_user>", "<db_pass>");
            $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

            } catch(PDOException $e){
                echo 'ERROR: ' . $e->getMessage();
                }

            $this->db = $conn;
    }

    public function getConnection(){
        return $this->db;
    }
}

I am Receiving the following error :

Fatal error: Call to undefined method PDO::bindParam() in ......... on line 22

If someone can help me out a bit that would be great, I really want to get to know PDo better.

Answer 1

You have to capture the result of the prepare call (which is a PDOStatement object) and then call bindParam() on that, not the PDO object itself.

$st = $this->db->prepare("SELECT * FROM users WHERE user_name=? and user_password=?");
$st->bindParam(1, $name);
$st->bindParam(2, $pass);
$st->execute();

$st is now the PDOStatement object and you can call bindParam() and execute() .

Answer 2

If you have copied your MySQL error to google you would see same errors in many many pages. Here is the first one saying:

The bindParam() method is inside the PDOStatement class, not the PDO class. The statement is the result of the prepare() method.

Please see: Call to undefined method PDO::bindParam()

Answer 3

You are using PDO object as statement prepared object to bind

$db = $this->db;
$st = $db->prepare("SELECT * FROM users WHERE user_name=? and user_password=?");
$st->bindParam(1, $name);
$st->bindParam(2, $pass);
$st->execute();