Array Assignment

I'm new to PHP (which will be obvious in just a minute). In Perl I can assign dynamic keys ad infinitum to an array such as: $sku{$id}{$line}{$price} = 99; But the syntax is escaping me for the same function in PHP. As I was trying to debug my thinking, I ran the following little test and am confused about the result. Two things: 1) Why does the code below produce this result? 2) How do I assign to an multidimensional array with dynamic keys? Here is the test code: $first = "Elementary"; $second = "Middle"; echo "before assignment:<BR>"; echo "first = $first<BR>"; // prints: first = Elementary echo "second = $second<P>"; // prints: second = Middle --- looks as expected here $first[$second] = "pass"; echo "After Assignment:<BR>"; echo "first = $first<BR>"; // prints: first = plementary --- what is this ????!! echo "second = $second<BR>"; // prints: second = Middle echo "$first[$second]"; // prints: P Thanks