多个密钥生成

I have code with me for key generation.

<?php   
function KeyGen()
{
 $keylength = 20;
 $key = md5(mktime());
 $new_key = '';
 for($i=1; $i <= $keylength; $i ++ )
    {
           $new_key .= $key[$i];
           if ( $i%5==0 && $i != $keylength) $new_key.='-';
    }
 return strtoupper($new_key);
 }
 echo KeyGen();
?>

i want to generate 20 keys. I am not getting how to do it.

  <?php   
 function KeyGen()
 {
 $keylength = 20;
 $key = md5(strtotime("now").rand());
 $new_key = '';
 for($i=1; $i <= $keylength; $i ++ )
   {
       $new_key .= $key[$i];
       if ( $i%5==0 && $i != $keylength) $new_key.='-';
   }
 return strtoupper($new_key);
 }
 $new_key= KeyGen();
 echo  $new_key;
 ?>

Call the function,You should get the key