How can PHP developers ensure their code is secure and follows modern standards, such as using isset() or empty() to test parameters?

PHP developers can ensure their code is secure and follows modern standards by properly validating user input and avoiding common vulnerabilities like SQL injection and cross-site scripting. One way to do this is by using isset() or empty() functions to test parameters before using them in the code, which helps prevent errors and improve code reliability.

// Example of using isset() to test if a parameter is set before using it
if(isset($_POST['username'])){
    $username = $_POST['username'];
    // Further processing of the username parameter
}
```

```php
// Example of using empty() to test if a parameter is empty before using it
if(!empty($_POST['email'])){
    $email = $_POST['email'];
    // Further processing of the email parameter
}