dynamic change array name?

[mshen]

I try to change a array name,but I do not work.Please help me.

Demo one

<?php
$a=100;
$b=a;
echo $$b
?>

output:100

Demo two

<?php
$a[0]=100;
$b=a;
echo $$b[0]
?>

do not work!!!why???

I need dynamic get the array name like demo two.please let me know how to do it.thanks

[mrskhris]

<?php
$a[0]=100;
$b="a";
echo ${$b}[0];
?>