Why the login page in PHP is not working? [closed]

index.php:

<?php
// index.php

session_start();

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    // Retrieve the submitted login form data
    $username = $_POST['username'];
    $password = $_POST['password'];

    // Validate the login credentials
    // Query the database to check if the username and password match
    // You'll need to replace 'citizens' with the actual table name and adapt the query accordingly

    // Assuming you're using MySQLi
    $mysqli = new mysqli('localhost', 'root', '', 'online_fir');

    $stmt = $mysqli->prepare("SELECT id, password FROM police WHERE Email = ?");
    $stmt->bind_param("s", $username);
    $stmt->execute();
    $stmt->store_result();

    if ($stmt->num_rows === 1) {
        // User found, verify the password
        $stmt->bind_result($id, $storedPassword);
        $stmt->fetch();

        if ($password === $storedPassword) {
            // Store relevant information in the session
            $_SESSION['user_id'] = $id;
            $_SESSION['username'] = $username;

            // Redirect the user to the welcome page or perform other actions
            header("Location: home.php");
            exit();
        }
    }

    // If the login credentials are invalid, show an error message or redirect back to the login page
    $error = "Invalid username or password.";
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>FIR</title>
    <link rel="stylesheet" href="css/style.css">
</head>
<body>
    <header>
        <div class="navbar">
            <a href="index.php">
                <div class="logo">
                    <img src="img/logo.jpg" alt="Logo" oncontextmenu="return false;">
                    <span class="logo-text">NYPD</span>
                </div>
            </a>
        </div>
    </header>

    <div class="login-container">
        <h2 class="login-title">Login</h2>
        <form method="POST" action="index.php">
            <div class="form-group">
                <label for="username">Username:</label>
                <input type="text" id="username" name="username">
            </div>

            <div class="form-group">
                <label for="password">Password:</label>
                <input type="password" id="password" name="password">
            </div>
            <div class="error">
                <?php if (isset($error)) { ?>
                <p<p style="color:red;"><?php echo $error; ?></p>
                <?php } ?>
            </div>
            <button type="submit">Login</button>
            <a href="register.php">Register User</a>
        </form>
    </div>
</body>
</html>

This is my code. Everything worked fine few days before. Now it’s not working. When I try to login, it says “Invalid username or password” even if the username and the password is correct. Anyone please help.

PS: I’m using XAMPP Server. And I’ve stored the password in the database as plain text.

I tried to login. But its not logging-in. It says “Invalid username or password” even if the username and the password is correct.