Wishes

What is the difference in meaning between these two sentences:
I wish I would have been there.
I wish I had been there.
If both are correct then why do we need two variants?
Thank you beforehand.

[Fizi]

'I wish I had been there' is correct usage in the Past Perfect.
'I wish I would have been there' is an incorrect mix.

'Would have' is used in the Past Conditional, such as
'Had I been there, I would have seen it'