Variable Variables and Mulitdimensional Arrays

Hi. I want to be able to access a key in a multidimensional array at some depth "n" without knowing before runtime what the keys are. I thought this might be possible using variable variables. Here's some sample code using variable variables and multidimensional arrays: $y = 'a'; $z = 'b'; $t = 'c'; $x = array("a"=>array("b"=>array("c"=>TRUE))); print_r($x{$y}{$z}{$t}); // Prints 1. // I want to be able to concatenate the array indexes into one variable variable. This would be done in a loop at runtime. $u = ${$y.$z.$t}; print_r($x{$u}); // Doesn't work. Any help would greatly be appreciated, Charlie