Commit session before HTTP redirection

I have different session save handler to meet the needs of the greatest number.
One of this session save handler stores session inside crypted cookie(s). The main advantage to store session in cookie is for architecture-less shared session between multi fontends.
But in order to work, session save handler must be able to write and close session but if header location is send cookies cannot be written

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`session_commit();` is an alias for `session_write_close();` that why I'm talking about commit inside title.