Description:
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session_start() fails on all but first request in session.


Reproduce code:
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I did a pecl install memcache (2.2.5) and added this to my app:

ini_set('session.save_handler', 'memcache');
ini_set('session.save_path', 'tcp://127.0.0.1:11211');

The first time a session is created, the page loads fine. Subsequent requests in the same session fail in session_start() with "Operation now in progress (36)".

I have isolated this problem to 2.2.5 by:
1) switching out the backend for toyko tyrant (which is memcache protocol compliant) -- same bug
1a) If I clear my session cookie it *works* the first time (although that does no good since it's a session).
2) downgrading to 2.2.4 -- works
3) I tried 3.0.4 but it wouldn't build so I didn't bother since 2.2.4 fixed it.

Expected result:
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Sessions should work.

Actual result:
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Subsequent requests in the same session fail in 
session_start() with "Operation now in progress (36)".