Correction : php5-fpm & MySQL : is not a valid MySQL-Link resource.

NOTE: fix things like this :
Warning:  mysql_select_db(): 2 is not a valid MySQL-Link resource in test.php
which is likely due to php5-fpm not correctly destroying all PHP variables ;
uses auto_prepend_file in php.ini :
- works when script ends or exit() is called;
- works when mysql.so is loaded or not;
- not sure if this works with multiple MySQL connexions.