Why and When Should You Explicitly Close MySQL Connections in PHP?

Importance of Closing MySQL Connections

Connections to a MySQL database consume resources on the server. Leaving connections open unnecessarily can lead to performance issues, especially on high-traffic websites. While MySQL automatically closes connections when a PHP script ends, it's crucial to close them explicitly for efficiency reasons.

When to Close Connections

According to the MySQL documentation:

"The link to the server will be closed as soon as the execution of the script ends, unless it's closed earlier by explicitly calling mysql_close()."

This means that if you're only retrieving data and performing minimal processing, the connection will automatically close when the script finishes. However, if you're performing extensive processing or retrieving large result sets, it's advisable to close the connection explicitly to conserve resources.

Effects of FastCGI

FastCGI (Fast Common Gateway Interface) is a protocol that improves PHP performance by keeping connections open. However, it's unclear whether fastcgi affects the behavior of mysql_connect regarding connection closure. While some sources suggest that fastcgi-enabled PHP creates persistent connections, others dispute this claim.

Best Practices

Regardless of the effects of fastcgi, the best practice is to use mysql_close() to close MySQL connections explicitly. Additionally, consider using PDO (PHP Data Objects) for database interaction, as it offers improved security and performance over the older mysql_* functions.

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