What security considerations should PHP developers keep in mind when working with links and actions in their code?

When working with links and actions in PHP, developers should always validate and sanitize user input to prevent vulnerabilities such as Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF). Additionally, it's important to use secure HTTPS connections for sensitive transactions and to implement proper access controls to restrict unauthorized actions.

// Example of validating and sanitizing user input for a link
$link = filter_var($_GET['link'], FILTER_SANITIZE_URL);
echo "<a href='" . $link . "'>Click here</a>";