Prime Number Hunter

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The following code is an Implementation of the Sieve of Eratosthenes in PHP. It's purpose is to sieve the natural numbers and separate the primes from the composites.

    function find_primes($number)
    {
        global $primes;
        
        $nlist = array();
        $sqrt = ceil(sqrt($number));

        $nlist[] = 2;
        $nlist[] = 3;
        for($i=5 ; $i < $number ; $i=$i+2)
        {
            if($i%3 != 0)
                $nlist[] = $i;
        }
        
        for($i=2,$divisor=5; $divisor < $sqrt ; $i++) {
           /*
            * Remove non primes numbers from an array ($nlist)
            * Non prime numbers are identified by dividing with a known
            * prime (the prime number in our array at $index)
            */
            $count = count($nlist);
            $j = $i*$i;
            $nlist2 = array_slice($nlist,0,$j);
            
            for( ; $j

This code is a memory hog. If you try it with large numbers you might see an error such as the following. If you do the solution is to use the ini_set function to increase the momory limit. Eg: ini_set('memory_limit','256M');

PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 35 bytes) in /home/raditha/euler.php on line 19