How can you validate and escape values in PHP to prevent errors like "Undefined index" and "Invalid arguments passed"?

To validate and escape values in PHP to prevent errors like "Undefined index" and "Invalid arguments passed", you can use functions like isset() to check if a variable is set and not null before accessing it, and functions like filter_var() to sanitize user input. By properly validating and escaping values, you can prevent errors and enhance the security of your application.

// Example of validating and escaping values in PHP
$variable = isset($_POST['input']) ? filter_var($_POST['input'], FILTER_SANITIZE_STRING) : '';