Is it possible to mend a serialize string that has become corrupted due to truncation?

I have a massive multidimensional array that has been serialised by PHP. It has been stored in MySQL and the data field wasn't large enough... the end has been cut off.

I need to extract the data, but unserialize wont work.

Does anyone know of a solution that can close all the arrays and recalculate the string lengths to produce a new valid serialized string?

It's too much data to do by hand.