PHP foreach loop on $_Request

Hello,

Ok, say you send this to a php page test.php

test.php?p=abc&w=erw&v1=123,122,342$v2=234,3123,3123&v3=34,3123,123

They get cleaned:
foreach (array_keys($_REQUEST) as $key) {
 $$key = $mysqli->real_escape_string(($_REQUEST[$key]));
 }

Now I have these:

$p,$w,$v1,$v2,$v3,$v4

Forget about the $p & the $w.

I want to now loop through only the $vx (where x is the number)

foreach(of-the-ones-the-start-with-a-v) {

$v=$the-one-used-in-this-loop;

      $arr=explode(',', $v);
      $first=$arr[0];
      $second=$arr[1];
      $third=$arr[2];

And now I do something with the $first,$second,$third

}


What needs to go here:

of-the-ones-the-start-with-a-v

And here:

$v=$the-one-used-in-this-loop;

Thank you for viewing my question, any help appreciated.