问两个数组PHP的所有组合

EN

   $digits = array(9,8,7,6,5,4,3,2,1);
   $primes = array(2,3,5,7,11);

   for ($first = 0; $first < count($digits)-1; $first++) {
         $num1 = $digits[$first];
      for ($second = 1; $second < count($digits)-2; $second++) {
         $num2 = $digits[$second];
            for ($third = 0; $third < count($primes)-1; $third++) {
         $num3 = $num1 * $primes[$third];
         $num4 = $num2 * $primes[$third];

         $questionlead = "Simplify <br>" .$num3. " : " . $num4 ;
         $ans = $num1. " : " . $num2 ;

   $dbhost = 'nope';
   $dbuser = 'notfor';
   $dbpass = 'you';

   $conn = mysql_connect($dbhost, $dbuser, $dbpass);

   if(! $conn ) {
      die('Could not connect: ' . mysql_error());
   }

   $sql = "INSERT INTO QuestionDB(TopicID, TopicName, SubtopicID, SubtopicName, Question, Answer, Difficulty, Author, Projectable) VALUES (6,'Ratio',1,'Simplifying ratio','".$questionlead. "','".$ans. "',1,'Richard Tock','Yes')";
   mysql_select_db('db_name');
   $retval = mysql_query( $sql, $conn );

   if(! $retval ) {
      die('Could not get data: ' . mysql_error());
   }

      }
}
}
   mysql_close($conn);
?>