What does the PDO::PARAM_EVT_* constants do?

I can't find any information on these constants but th开发者_如何学Pythone sparse bit the documentation gives.

What can they be used for, and do I to use them?

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As far as I can tell, you cannot use them as an end-user. Those constants are used internally on a per-driver basis for handling of the events described. Browsing the source at http://svn.php.net/repository/php/php-src/branches/PHP_5_3/ext/ I did not find any end-user functionality.