You're thinking about implementation igbinary for serialize/unserialize function (at least in optional or autodetect) ?
My tests showing better resolution in execution time and memory consumption.
(for huge array)
Serialize: 1245.229ms
serialize string strlen 34572639
Unserialize: 2040.023ms

IGBinary Serialize: 492.500ms
serialize string strlen 5736402
IGBinary Unserialize: 837.035ms