MySQL
PHP Manual

MySQL Native Driver

User Contributed Notes

juangiordana at gmail dot com 15-Jan-2011 02:55
Notice that since of PHP 5.3.0 there is no need to set 'default_socket_timeout to -1'.

"The MySQL Client Library sets a default timeout of 365 * 24 * 3600 seconds (1 year) and waits for other timeouts to occur, such as TCP/IP timeouts. mysqlnd now uses the same very long timeout."

http://www.php.net/mysqlnd.config.php#mysqlnd.net_read_timeout
koalay at gmail dot com 16-Sep-2009 07:53
For those who manually compiled MySQL, the default
 mysqlnd settings may results in error.
Your mysql_error() function may give you this message:

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No such file or directory (trying to connect via unix:///tmp/mysql.sock)
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This is because your manually compiled MySQL has its own place for socket.
You need to provide PHP a reference for an appropriate mysql socket.
That means you need to edit php.ini and add a section like this:

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[mysql]
mysql.default_socket="/your/path/to/mysql.sock"
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eric dot caron at gmail dot com 02-Sep-2009 06:59
One important part of the MySQL Native Driver, which is overlooked, is that when connecting to MySQL via a socket, the connection is subject to the "default_socket_timeout" value.

This means that if you have the default_socket_timeout set to 60 (default value), and you have a query that takes longer than 60 seconds to respond, the connection will be severed and getting the query results will fail.

The solution (as of PHP 5.3.0) is to change default_socket_timeout to -1 in php.ini, or with ini_set.

MySQL
PHP Manual