Php

<?php
    $host = "localhost";
    $username = "root";
    $password = "";
    $database = "PDOtesting";
    $message = "";
    try
    {
      $connect = new PDO("mysql:host=$host; dbname=$database", $username, $password);
      $connect->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

        if(isset($_POST['re_password'])) {

            $old_pass=$_POST['old_pass'];
            $new_pass=$_POST['new_pass'];
            $re_pass=$_POST['re_pass'];

            // User confirm old password authentication
                $query = "SELECT * FROM users WHERE username = :username LIMIT 1";
                $statement = $connect->prepare($query);
                $statement->execute(
                     array(
                          'username'     =>     $login_session
                     )
                );
                $count = $statement->rowCount();

                if($count > 0)
                {
                     $result = $statement->fetch();

                    //check old password if correct
                    if (password_verify($_POST["old_pass"], $result['old_pass'])) {
                         // if password correct
                        if ($new_pass == $re_pass) {

                            $query2 = "UPDATE users SET password = :password WHERE username = :username";

                            $hash = password_hash($re_pass, PASSWORD_DEFAULT);

                            $statement = $connect->prepare($query2);
                            $statement->execute(
                                array(
                                    'username'     =>     $login_session,
                                    'password'     =>     $hash
                                )
                            );

                            echo "<script>alert('Changed Password Sucessfully! You will be logged out from this page'); window.location='../session_destroy.php'</script>";

                        }

                        else {
                            echo "<script>alert('new password and repeat password does not match!'); window.location='change_password.php'</script>";
                        }
                    }} else {
                        echo "<script>alert('Your old password is incorrect'); window.location='change_password.php'</script>";
                    }

                // $data_pwd=$chg_pwd1['password'];
        }
    }
    catch(PDOException $error)
    {
      $message = $error->getMessage();
    }
    ?>