What is the difference between MySQL and MySQLi ?
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In relation to programming in PHP language, both MySQLi and MySQL are ways or interfaces to connect to the database. There's not much difference between the two interfaces.
But when someone uses MySQLi in Joomla, he/she will have more features since MySQLi is the improved version of MySQL.
MySQLi supports MySQL API features like prepared and multiple statements & transactions. It has also an enhanced capability for debugging and the interface of MySQLi is object-oriented.
However, even if MySQLi has these features and has an object-oriented interface, MySQL is slightly faster in performance especially in list queries.
See this link for more info about different between MySQL and MySQLi
Hope this answers your question.
The mysqli is an extension used in MySQL. The PHP code consists of a core, with optional extensions to the core functionality. Another extension is called mysql extension.
Both mysqli extension and mysql extension are implemented using the PHP extension framework. An extension typically exposes an API to the PHP programmer to allow its facilities to be used programmatically.
However, some extensions which use the PHP extension framework do not expose an API to the PHP programmer.
The mysqli extension is also known as MySQL improved and was developed to take advantage of new features found in MySQL systems versions 4.1.3 and later.
The mysqli extension is included with PHP versions 5 and later. Here are some of the benefits of mysqli extension: