Using Persistent Connections If mysqli is used with mysqlnd, when a persistent connection is created it generates a COM_CHANGE_USER (mysql_change_user()) call on the server. This ensures that re-authentication of the connection takes place. As there is some overhead associated with the COM_CHANGE_USER call, it is possible to switch this off at compile time. Reusing a persistent connection will then generate a COM_PING (mysql_ping) call to simply test the connection is reusable. Generation of COM_CHANGE_USER can be switched off with the compile flag MYSQLI_NO_CHANGE_USER_ON_PCONNECT. For example: Or alternatively: Note that only mysqli on mysqlnd uses COM_CHANGE_USER. Other extension-driver combinations use COM_PING on initial use of a persistent connection.