I know I this is simple, but i just can;t find the resource that tells me how to do it.
SO my code is as follows:
session_start();
$wquery=
"select week_num,week_name
from stats_week
where season=$this_season
order by week_num";
    $wresult=mysql_query($wquery);
print'<form action="changeplayer_2.php" method="post">';
        print"<select name='Week_select'> <br>";
        while ($wrow=mysql_fetch_array($wresult))
    { 
    print '<option value="'.$wrow['week_num'].'">'.'week '.$wrow['week_num'].'     '.$wrow['week_name'].'</option><br>\n';  
    }
print "</select><br><br>";#
    print'<button type="submit" >Next</button>';
    print"</form>";
So I am making a selection: I want that selection to end up in: $_SESSION['week']