Manual:$wgSessionHandler

Cookies: $wgSessionHandler
Used to set PHP's session.save_handler.
Introduced in version:1.16.0 (r49370)
Deprecated in version:1.27.0 (Gerrit change 267737; git #2257fe42)
Removed in version:1.33.0 (Gerrit change 489405; git #a38fe6cd)
Allowed values:(string) or null
Default value:null (1.18-1.32)
'files' (1.16-1.17)

Details

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This is used for setting PHP's session.save_handler. In practice, you will almost never need to change this ever. Other options might be 'user' or 'session_mysql'.

Setting to null skips setting this entirely (which might be useful if you're doing cross-application sessions, see bug 11381).