ext/standard Deprecate passing empty string to realpath()

[arshidkv12]

Deprecate passing an empty string to the realpath() php function.

Passing an empty string to realpath() currently resolves to the current working directory. This behavior is implicit and not
self-explanatory.

Deprecate this usage and emit E_DEPRECATED, recommending getcwd() instead for retrieving the current working directory.

[devnexen]

Deprecate passing an empty string to the realpath() php function.

Deprecation decision needs to be discussed a little.

Passing an empty string to realpath() currently resolves to the current working directory. This behavior is implicit and not self-explanatory.

But is documented behavior.

Deprecate this usage and emit E_DEPRECATED, recommending getcwd() instead for retrieving the current working directory.

[arshidkv12]

@devnexen Okay

[iluuu1994]

Seems like an unnecessary BC break, in my opinion. Especially if this is documented, people may rely on this behavior.