PHP Symbol Table

Question

According to the image description, when the second value of the array is changed using one of its two references, the array's reference counting the symbol table is set to 1.The reason for this is that a new array was allocated in memory after the second value was changed using one of the references. However, I wonder if this could happen to variables referencing scalar primitives such as integers, floating-point numbers, Strings, and Booleans or is it only limited to compound primitives such as arrays?