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    <p>I just read this comment on PHP website regarding persistent connection and it might be interesting to know:</p> <blockquote> <p>Here's a recap of important reasons NOT to use persistent connections:</p> <ul> <li><p>When you lock a table, normally it is unlocked when the connection closes, but since persistent connections do not close, any tables you accidentally leave locked will remain locked, and the only way to unlock them is to wait for the connection to timeout or kill the process. The same locking problem occurs with transactions. (See comments below on 23-Apr-2002 &amp; 12-Jul-2003)</p></li> <li><p>Normally temporary tables are dropped when the connection closes, but since persistent connections do not close, temporary tables aren't so temporary. If you do not explicitly drop temporary tables when you are done, that table will already exist for a new client reusing the same connection. The same problem occurs with setting session variables. (See comments below on 19-Nov-2004 &amp; 07-Aug-2006)</p></li> <li><p>If PHP and MySQL are on the same server or local network, the connection time may be negligible, in which case there is no advantage to persistent connections.</p></li> <li><p>Apache does not work well with persistent connections. When it receives a request from a new client, instead of using one of the available children which already has a persistent connection open, it tends to spawn a new child, which must then open a new database connection. This causes excess processes which are just sleeping, wasting resources, and causing errors when you reach your maximum connections, plus it defeats any benefit of persistent connections. (See comments below on 03-Feb-2004, and the footnote at <a href="http://devzone.zend.com/node/view/id/686#fn1" rel="nofollow noreferrer">http://devzone.zend.com/node/view/id/686#fn1</a>)</p></li> </ul> </blockquote> <p>(I was not the one that wrote the text above)</p>
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    1. POPHP mySQL - When is the best time to disconnect from the database?
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    1. USRicardo Amaral
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    1. COWhere did that come from? Copying from elsewhere without so much as a citation is not proper.
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      1. USAndrew Medico
    2. COThere's information built on thoroughly out of date versions of mysql in there. I would view it skeptically. Also with regard to PHP.
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      1. USdkretz
    3. COIn addition to temp tables, don't forget MySQL user variables, session settings like CHARSET, and LAST_INSERT_ID(). These are scoped to the connection, so the next web request that gets that persistent connection may "see" the state of another user's DB session!
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      1. USBill Karwin
 

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