PHP code:

    class Rsa {

        /** THE RSA ALGORITHM
        * The RSA is an encryption algorithm invented by Rivest, Shamir and Adleman.
        * RSA uses a public (open) and a private (secret) key. 
        * The public key is used to encrypt messages, but only the private key can decrypt them.
        * This works the other way around, too: messages encrypted with the private key can only
        * be decrypted with the public key.
        *
        * Generating the keys:
        * First we randomly choose two distinct prime numbers, p and q.
        * We multiply p and q to get the modulo, n.
        * Then calculate public key e where a whole number 1 < e < n which  in turn is coprime with (p-1)*(q-1)
        * If e is prime it will take less calculations on client side
        * Calculate private key d so that e * d mod (p-1)*(q-1) = 1
        * p and q are not stored to remove any evidence which could lead to breaking the cipher
        */

          public function generate_keys ()
          { 
                global $primes,  $maxprimes; 
                
                //Primes array
                $primes = array (4507,  4513,  4517,  4519,  4523,  4547,  4549,  4561,  4567,  4583,  4591,  4597, 
                4603,  4621,  4637,  4639,  4643,  4649,  4651,  4657,  4663,  4673,  4679,  4691,  4703,  4721,  4723,  4729,  4733,  4751, 
                4759,  4783,  4787,  4789,  4793,  4799,  4801,  4813,  4817,  4831,  4861,  4871,  4877,  4889,  4903,  4909,  4919,  4931, 
                //snipped for brevity

                //Set a random number picker for choosing the primes
                mt_srand((double)microtime()*1000000); 

                $maxprimes = count($primes) - 1; 
                $p = $primes[mt_rand(0,  $maxprimes)]; 
    
                while (empty($q) || ($p==$q)) $q = $primes[mt_rand(0,  $maxprimes)];

                $n     = $p*$q;
                $pi    = ($p - 1) * ($q - 1);
                $e     = $this->tofindE($pi,  $p,  $q);
                $d     = $this->extend($e, $pi);
                $keys  = array ($n, $e, $d);  

                //Return the array $keys[modulo, public key, private key]
                return $keys; 
            }