<?php

// Establishing Connection with Server by passing server_name, user_id and password as a parameter
$connection = mysql_connect("localhost", "root", "");
// Selecting Database
$db = mysql_select_db("cavallo", $connection);
session_start(); // Starting Session
// Storing Session
$user_check = $_SESSION['login_user'];
// SQL Query To Fetch Complete Information Of User
$ses_sql = mysql_query("select username from login where username='$user_check'", $connection);
$row = mysql_fetch_assoc($ses_sql);
$login_session = $row['username'];
if (!isset($login_session)) {
    mysql_close($connection); // Closing Connection
    header('Location: index.php'); // Redirecting To Home Page
}
?>

//setting up connection
$dbconn = new PDO('mysql:dbname=dbname;host=127.0.0.1;charset=utf8', 'root', '');
//prepare query
$user_check=$_SESSION['login_user'];
$prepareQuery = $db->prepare('INSERT INTO table (column) VALUES (:column)');

$perpareQuery->execute(array('column' => $user_check));

foreach($perpareQuery as $row) {

 }

$password = $_POST['password'];
$password = hash('sha256',$password);

$username = $_POST['username'];
$password = $_POST['password'];

settype($username,"string");
$password = hash('sha256',$password);

$stmt = $dbConnection->prepare('SELECT * FROM login WHERE username = ? and password = ?');
$stmt->bind_param('s', $username,$password);

$stmt->execute();

$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    // do something with $row
}