How can one effectively modify PHP code to remove or customize a login section on a website?

To remove or customize a login section on a website, you can modify the PHP code by either commenting out the login section or replacing it with custom HTML and CSS. This can be done by locating the relevant PHP file that controls the login section, such as header.php or functions.php, and making the necessary changes.

```php
// Example of commenting out the login section in header.php
// <div class="login-section">
//    <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>
```
This code snippet demonstrates how to comment out the login section in the header.php file by wrapping the login section HTML code in comment tags. This will effectively remove the login section from the website.