close mysql connection important?

Question

is it crucial to close mysql connections efficiency wise? or does it automatically close after php file is run?

Answer 1

From the documentation:

Note: 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().

If your script has a fair amount of processing to perform after fetching the result and has retrieved the full result set, you definitely should close the connection. If you don't, there's a chance the MySQL server will reach it's connection limit when the web server is under heavy usage. If you can't close the MySQL connection until near the end of the script, it's cleaner though unnecessary to do so explicitly.

I'm not certain how fastcgi affects things. One page claims that a build of PHP that supports fastcgi will create persistent connections, even for mysql_connect. This contradicts the documentation in that the connection is closed when the process, rather than the script, ends. Rather than testing it, I'm going to recommend using mysql_close(). Actually, I recommend using PDO, if it's available.

Answer 2

When using something like cgi, it's completely unnecessary to close your mysql connections since they close automatically at the end of script execution. When using persistent technologies like mod_perl and others, which maintain your connections between requests, then it's important to keep track of connections, global variables, etc..

Basically, for persistent data, clean up after yourself. For trivial, non-persistent data, it'll all go away when the request finishes anyway. Either way, best practice is to always close your connections.

Answer 3

Is it crucial? Not so much

Is it considered to be a good practice to follow? Yes.

I don't see why you wouldn't want to close it.

Answer 4

See this question too

http://stackoverflow.com/questions/336078/php-mysql-when-is-the-best-time-to-disconnect-from-the-database

Answer 5

when you have an embedded javascript code from other sites in security reasons is better you close database connection

Answer 6

Gets closed as soon as the script completes execution. Unless you've opened a persistent connection. Ideally you should release a resource (a connection here) as soon as you are done with it. Unless there is a good chance that you will be needing it again very soon in the execution.

Connection pooling or using persistent connections (if that's what you meant) is a good idea if you are behind a single database server. However if there are more servers and you are load balancing, it might hurt the distribution of work. Typically some clients run heavy queries while others run lighter ones. So if the same connection is used over n over, some servers would hit heavy load while others would be under utilized. Consider using smaller ttls and variable connection pool size.