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Explicitly closing open connections and freeing result sets is optional. However, it's a good idea to close the connection as soon as the script finishes performing all of its database operations, if it still has a lot of processing to do after getting the results.
To close the connection in mysql database we use php function mysqli_close() which disconnect from database. It require a parameter which is a connection returned by the mysql_connect function. Syntax: mysqli_close(conn);
What is the difference between mysql and mysqli? Basically, MySQL is the old database driver, and MySQLi is the Improved driver. The "i" stands for "improved" so it is MySQL improved. MySQLi can be done procedural and object-oriented whereas MySQL can only be used procedurally.
MySQLi supports both procedural interfaces and object oriented interfaces while MySQL supports only procedural interfaces. MySQLi supports stored procedure but MySQL does not. There is enhanced security and improved debugging features in MySQLi where this is comparatively lagging in MySQL.
If you have a look at MySQL Improved Extension Overview, it should tell you everything you need to know about the differences between the two.
The main useful features are:
There is a manual page dedicated to help choosing between mysql, mysqli and PDO at
The PHP team recommends mysqli or PDO_MySQL for new development:
It is recommended to use either the mysqli or PDO_MySQL extensions. It is not recommended to use the old mysql extension for new development. A detailed feature comparison matrix is provided below. The overall performance of all three extensions is considered to be about the same. Although the performance of the extension contributes only a fraction of the total run time of a PHP web request. Often, the impact is as low as 0.1%.
The page also has a feature matrix comparing the extension APIs. The main differences between mysqli and mysql API are as follows:
mysqli mysql
Development Status Active Maintenance only
Lifecycle Active Long Term Deprecation Announced*
Recommended Yes No
OOP API Yes No
Asynchronous Queries Yes No
Server-Side Prep. Statements Yes No
Stored Procedures Yes No
Multiple Statements Yes No
Transactions Yes No
MySQL 5.1+ functionality Yes No
* http://news.php.net/php.internals/53799
There is an additional feature matrix comparing the libraries (new mysqlnd versus libmysql) at
and a very thorough blog article at
I have abandoned using mysqli. It is simply too unstable. I've had queries that crash PHP using mysqli but work just fine with the mysql package. Also mysqli crashes on LONGTEXT columns. This bug has been raised in various forms since at least 2005 and remains broken. I'd honestly like to use prepared statements but mysqli just isn't reliable enough (and noone seems to bother fixing it). If you really want prepared statements go with PDO.
MySQLi stands for MySQL improved. It's an object-oriented interface to the MySQL bindings which makes things easier to use. It also offers support for prepared statements (which are very useful). If you're on PHP 5 use MySQLi.
What is better is PDO; it's a less crufty interface and also provides the same features as MySQLi.
Using prepared statements is good because it eliminates SQL injection possibilities; using server-side prepared statements is bad because it increases the number of round-trips.
for me, prepared statements is a must-have feature. more exactly, parameter binding (which only works on prepared statements). it's the only really sane way to insert strings into SQL commands. i really don't trust the 'escaping' functions. the DB connection is a binary protocol, why use an ASCII-limited sub-protocol for parameters?
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