What does the PHP function !isset do and how is it related to password verification?

The PHP function !isset checks if a variable is not set or is null. In the context of password verification, it can be used to ensure that the password input field is not empty before proceeding with the verification process. By using !isset, we can prevent the verification process from happening if the password field is empty, thus improving the security of the application.

if(isset($_POST['password'])) {
    $password = $_POST['password'];
    
    if(!isset($password) || empty($password)) {
        echo "Please enter a password.";
    } else {
        // Proceed with password verification process
    }
}