<?      
    $number  =  rand(1,6);
?>
        .......
 
        <FORM METHOD = "GET" ACTION = "someOther.php">

        <INPUT TYPE = "HIDDEN" NAME = "$num" VALUE = "<?= $number ?>">      
        <BR><BR>
        <INPUT TYPE = "SUBMIT" VALUE = "send">
        </FORM>

<?      
    $number  =  rand(1,6);
?>
        .......
 
        <FORM METHOD = "GET" ACTION = "someOther.php">

        <INPUT TYPE = "HIDDEN" NAME = "$num" VALUE = "<? echo $number ?>">      
        <BR><BR>
        <INPUT TYPE = "SUBMIT" VALUE = "send">
        </FORM>