How can CSS styling be properly applied to a login window in PHP to ensure a clean and consistent appearance?

To ensure a clean and consistent appearance of a login window in PHP, CSS styling can be applied by creating a separate CSS file and linking it to the PHP login page. This allows for easy management of styles and ensures a consistent look across all pages. Additionally, using classes and IDs in the HTML elements of the login window can help target specific elements for styling.

<!DOCTYPE html>
<html>
<head>
    <title>Login Page</title>
    <link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>

<div class="login-container">
    <h2>Login</h2>
    <form action="login.php" method="post">
        <input type="text" name="username" placeholder="Username">
        <input type="password" name="password" placeholder="Password">
        <button type="submit">Login</button>
    </form>
</div>

</body>
</html>
```

CSS file (styles.css):
```css
.login-container {
    width: 300px;
    margin: 0 auto;
    padding: 20px;
    border: 1px solid #ccc;
    border-radius: 5px;
}

input {
    width: 100%;
    padding: 10px;
    margin: 5px 0;
    border: 1px solid #ccc;
    border-radius: 5px;
}

button {
    width: 100%;
    padding: 10px;
    margin: 5px 0;
    border: none;
    border-radius: 5px;
    background-color: #007bff;
    color: #fff;
    cursor: pointer;
}