What are the potential pitfalls of using shell_exec() in PHP?

Using shell_exec() in PHP can be dangerous as it allows for the execution of shell commands on the server, potentially opening up security vulnerabilities such as command injection attacks. To mitigate this risk, it is recommended to sanitize user input and validate commands before using shell_exec(). Additionally, consider using alternative methods like PHP's built-in functions for executing commands safely.

$user_input = $_POST['user_input'];
$validated_input = escapeshellarg($user_input);
$output = shell_exec("ls " . $validated_input);
echo $output;