mysqli

MySQLi, short for MySQL Improved, is a PHP extension that provides an interface for interacting with MySQL databases. It was introduced to replace the older ext/mysql extension and to offer enhanced features and security. MySQLi supports both procedural and object-oriented programming styles, allowing developers to use either functions or a MySQLi class instance to perform queries.

Key features include prepared statements with parameter binding (via bind_param and bind_result), which help prevent SQL injection and improve performance for repeated queries. The extension also supports transactions (autocommit, commit, rollback), as well as multi-query execution (mysqli_multi_query) and stored procedures. It exposes methods for retrieving results (fetch_assoc, fetch_object, etc.), managing connections, and querying server information. MySQLi connections can specify character sets and can use SSL, and persistent connections are possible with a p: prefix on the host.

MySQLi is specific to the MySQL server family, in contrast to PDO_MySQL, which is the database-agnostic option in PHP. It is commonly chosen when MySQL-specific features such as prepared statements and advanced result handling are needed. The old MySQL extension, mysql_, has been deprecated and removed in PHP 7; current PHP applications are advised to use MySQLi or PDO_MySQL.