Dynamically named variables and arrays.

I know this works: $varName = 'bob'; ${$varName} = 'joe'; Now, what I'm hoping to to is take the same premis and apply it to arrays (particularly POST). What I'm doing is creating form element names as follows: sales_data[area][1] sales_data[area][2] ... sales_data[area][5] and so on. Upon form submission, we all know that PHP turns the above into an array that I can iterate through and get the values. Now, I now the names of the form elements. So using that, I'm trying to access the value of the outermost element dynamically. To do that, I'm doing: <script language="php"> $requiredPostFieldName = str_replace( "sales_data", "", "sales_data[area][2]" ); $fieldVal = ${"_POST['sales_data']{$requiredPostFieldName }"}; </script> But that's not working. Should it? Am I doing something wrong? Any ideas or suggestions would be very much appreciated! Christoph