[single-choice] about PHP reference, the error is

[single-choice] for PHP reference, the error is:

2. Unset a reference, just breaking the binding between the variable name and the variable content, does not mean that the contents of the variable are destroyed.
4. PHP reference is essentially a pointer, which can be bound to other variables within the scope of the function call.
6. in the method of an object, $this is always a reference to the object that called it.
8. You can pass a variable to a function by reference, so that the function can modify the value of its argument.

Correct answer:
I'm sorry, I didn't answer it.

The answer resolution reference is just the alias of the value memory block, and the pointer is an entity that holds the value memory address, which requires additional memory space.

[single-choice] about PHP reference, the error is