prime numbers

prime.php

<?php

/**
 * @param $number
 * @return bool
 */
function is_prime($number)
{
    if ($number < 2) {
        return false;
    }

    if ($number === 2)
        return true;

    if ($number % 2 === 0)
        return false;

    $sqrt = ceil(sqrt($number));

    for ($i = 3; $sqrt < $i; $i += 2) {
        if ($number % $i === 0) {
            return false;
        }
    }

    return true;

}