Hello, and welcome back! Are you ready for a new challenge? In this unit, we're stepping up a notch to tackle a complex yet intriguing task. It involves parsing complex strings into PHP associative arrays and then updating them, which is a common requirement in many real-world tasks. So yes, this unit's session is going to be pretty pragmatic — just the way you like it!

This task involves transforming a given string into a nested PHP associative array and updating a specific key-value pair within that array. The input string will take the form "Key1=Value1,Key2=Value2,...". When a part of the value is another key-value string, we create a nested associative array.

For example, the string "A1=B1,C1={D1=E1,F1=G1},I1=J1" should be transformed into the following nested associative array:

Your PHP function should parse this string into the above associative array, then update the value of the nested key F1 from G1 to some other value, say NewValue. The function should ultimately return the updated associative array.

First, set up the function and necessary variables: