Dfyjkt

I am a newbie and I was trying to create a login system using PHP and Mysql. After finishing registration form and adding few users, I was trying to create a login form. but it always returns false saying my your Your username or password is incorrect!. Below is my code. It will be great if someone could help me. Advance sorry if my doubt is tooo basic :/

<?php
 session_start();
 include '.includesfunctionsdb.php';
?>

<?php
 $username = strtolower(mysqli_real_escape_string($db, $_POST['username']));
 $password = strtolower(mysqli_real_escape_string($db, $_POST['password']));

 $sql = "SELECT * FROM users WHERE username = '$username' ";
 $result = mysqli_query($db, $sql);
 $row = mysqli_fetch_assoc($result);
 $hash_pwd = $row['password'];
 echo $hash_pwd;
 echo $password;
 $hash = password_verify($password, $hash_pwd);

 if ($hash ==0) 
 header("Location: ./index.php?error=check");
 exit();
 else 
 $sql = "SELECT * FROM user WHERE username = '$username' AND password = '$hash_pwd'";
 $result = mysqli_query($db, $sql);
 if (mysqli_num_rows($result) == 0) 
 echo "Your username or password is incorrect!";
 else 
 $_SESSION['id'] = $row['id'];
 $_SESSION['username'] = $row['username'];
 
 //header("Location: ./index.php");
 
?>

and my registration page is as follows

<?php
//This Page is for registration of users
?>

<?php
// this php tag is for all includes
include '.includesfunctionsdb.php';

?>

<?php
//print isset($_POST["submit"]);
//Getting all details inserted in form
if(isset($_POST["register"]))
 $username = $_POST['username'];
 $firstname = $_POST['firstname'];
 $lastname = $_POST['lastname'];
 $email = $_POST['email'];
 $password = $_POST['password'];
 $date = date('Y-m-d H:i:s');

 //Encrypting and Securing recieved data
 $username = strtolower(mysqli_real_escape_string($db, $username));
 $firstname = strtolower(mysqli_real_escape_string($db, $firstname));
 $lastname = strtolower(mysqli_real_escape_string($db, $lastname));
 $email = strtolower(mysqli_real_escape_string($db, $email));
 $password = strtolower(mysqli_real_escape_string($db, $password));
 $encryptedpassword = password_hash($password, PASSWORD_DEFAULT);

 //To check duplication of email ids
 $sql = "SELECT email FROM users WHERE email='$email'";
 $result = mysqli_query($db, $sql);
 $row = mysqli_num_rows($result);//$row will return count of rows if any duplicate email ids are found

 //To check duplication of usernames
 $sql2 = "SELECT username FROM users WHERE username='$username'";
 $result2 = mysqli_query($db, $sql2);
 $row2 = mysqli_num_rows($result2);//$row2 will return count of rows if any duplicate usernames are found

 //conditions to check what all duplicates are found
 if($row > 0 && $row2 >0)
 echo "Sorry...This email id and username is already taken!!!";
 elseif ($row > 0 ) 
 echo "Sorry...This email id is already taken!";
 elseif ($row2 > 0) 
 echo "Sorry...This Username is already taken!";
 else 
 $query = mysqli_query($db, "INSERT INTO users (username, firstname, lastname, password, email, regdate) VALUES
 ('$username', '$firstname', '$lastname', '$encryptedpassword', '$email', '$date')");
 if($query)
 echo "Thank You! you are now registered.";
 
 


?>

The error in my code is because of password = '$hash_pwd' condition in my where clause. When i retried row with given username and later verified password using php, it works as intended. I guess password hashed in php using password_hash() cannot be retrived and verified like encryption. Anyway thanks for all of yours responses