Random script issues

[Delusion]

Hello,

Generally, I'll describe what was my idea at first.

I've been trying to make a script for my school (football, 1vs1) that will make me random teams selection.

The main idea about it, I got 11 teams, The random I was trying to do:

Each team should play 20 games in a season, with each team playing each other TWICE at a season.

I've tried to make this using a 'FOR' loops but I've got double games and alot of mess.

Here's my try:

<?
echo "<table>";
 for($i=1 , $c=1 , $b=4 , $a=1 ; $i <= 220 ; $i++ , $c+=1 , $b++, $a++) {

   echo "<tr>";
     echo "<td width='100' align='left'>$i</td>";
     echo "<td>team $a</td>";
     echo "<td>vs.</td>";
     echo "<td>team $b</td>";
   echo "</tr>";

  // Storing the DATA at MySQL irrelevant now

   if ($a >= "11") { $a = "0"; }
   if ($b >= "11") { $b = "0"; }
   if ($c >= "6") { $c = "0"; echo "<tr><td colspan='5'><hr></td></tr>"; }
 }

echo "</table>";

I've spent alot of time trying to make it work and failed
I hope someone around will be able helping me!

Thanks in advnace.