PHP - check if number is prime

Question

I\'m trying to create a function which checks whether the number is prime or not. BUT I want this function to echo to the user \'prime\' or \'NOT prime\' - and that\'s where my

Answer 1

function is_prime($number)
{
    return (bool) !preg_match('/^1?$|^(11+?)\1+$/x', str_repeat('1', $number));
}