What potential pitfalls should be avoided when using the exec function in PHP?

One potential pitfall when using the exec function in PHP is the risk of command injection vulnerabilities if user input is not properly sanitized. To mitigate this risk, always validate and sanitize user input before passing it to the exec function. Additionally, avoid using user input directly in the command string passed to exec.

// Example of avoiding command injection vulnerability with exec function
$user_input = $_POST['input'];
$validated_input = escapeshellarg($user_input); // Sanitize user input
exec("ls " . $validated_input);