primes.php

<?php

/**
 * Alternative prime number generator
 *
 * Generates first <n> prime numbers using 
 * the prime numbers themselves
 *
 * @author Jitendra Adhikari <jiten.adhikary@gmail.com>
 *
 * @param  int   The number of prime numbers to generate
 * @return array The generated prime numbers
 */
function primes($n)
{
    static $p = [2];
    if (count($p) >= $n) {
        return array_slice($p, 0, $n);
    }

    $i = end($p);
    while ($i++) {
        foreach ($p as $_p) {
            if ($i % $_p == 0) {
                continue 2;
            }
        }
        $p[] = $i;
        if (count($p) == $n) {
            return $p;
        }
    }
}