SQLSTATE[HY093]: Invalid parameter number: parameter was not defined # - php

Question

I am writing some code to interact with a login database on phpmyadmin through the following code.
However, I get the following error, it doesn't specify which line the error occurs at. It's been bugging me for 3 days, and my researches didn't lead to any solution. Just in case : SQLSTATE[HY093]: Invalid parameter number: parameter was not defined
Can someone help me pinpoint the problem please?
Thank you in advance.
<?php
session_start();
$user_name = "test" ;
$user_password = "test";
/* Login to database */
$DB_name = "adaming_login_db";
$DB_user = "root";
$DB_pass = "";
$DB_host = "localhost";
try
{
$DB_con = new PDO("mysql:host={$DB_host};dbname={$DB_name}",$DB_user,$DB_pass);
$DB_con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
echo $e->getMessage();
}
class USER
{
private $db;
public function __construct($DB_con)
{
$this->db = $DB_con;
}
public function login($user_name,$user_password)
{
try
{
$stmt = $this->db->prepare("SELECT * FROM login_info WHERE user_name = :$user_name AND user_password = :$user_password");
$stmt->execute(array(':user_name'=>$user_name, ':user_password'=>$user_password));
$userRow=$stmt->fetch(PDO::FETCH_ASSOC);
if($stmt->rowCount() > 0)
{
if($user_password == $userRow['user_password'] && $user_name == $userRow['user_name'] )
{
$_SESSION['user_session'] = $userRow['user_id'];
echo "Success";
return true;
}
else
{
echo "Failed";
return false;
}
}
}
catch(PDOException $e)
{
echo $e->getMessage();
}
}
}
$user = new USER($DB_con);
$user->login($user_name,$user_password);
?>

Answer 1

You need to remove dollar signs from your query. Change:
$stmt = $this->db->prepare("SELECT * FROM login_info WHERE user_name = :$user_name AND user_password = :$user_password");
to
$stmt = $this->db->prepare("SELECT * FROM login_info WHERE user_name = :user_name AND user_password = :user_password");