double $

<? // this example is about double$ or more
$bye=astalavista;
$d=bye;
print $$d;
/*you will see astalavista on browser
because $$d=${$d}=$bye=astalavista
*/
?>
<br />
<? //this is another example it follows reverse...
$tic=tac;
$$tic=tictac;
print $tac;
//tictac=$$tic=${$tic}=$tac
//You will see tictac on your browser.
?>
Here explained double $ string....