The mysqli extension was introduced with PHP version 
  5.0.0. The MySQL Native Driver was included in PHP version 5.3.0.
 
The common Unix distributions include binary versions of PHP that can be installed. Although these binary versions are typically built with support for the MySQL extensions, the extension libraries themselves may need to be installed using an additional package. Check the package manager that comes with your chosen distribution for availability.
   For example, on Ubuntu the php5-mysql package installs
   the ext/mysql, ext/mysqli, and pdo_mysql PHP extensions. On CentOS, 
   the php-mysql package also installs these three 
   PHP extensions.
  
Alternatively, you can compile this extension yourself. Building PHP from source allows you to specify the MySQL extensions you want to use, as well as your choice of client library for each extension.
The MySQL Native Driver is the recommended client library option, as it results in improved performance and gives access to features not available when using the MySQL Client Library. Refer to What is PHP's MySQL Native Driver? for a brief overview of the advantages of MySQL Native Driver.
   The /path/to/mysql_config represents the location of
   the mysql_config program that comes with MySQL
   Server.
  
| PHP Version | Default | Configure Options: mysqlnd | Configure Options: libmysqlclient | Changelog | 
|---|---|---|---|---|
| 5.4.x and above | mysqlnd | --with-mysqli | --with-mysqli=/path/to/mysql_config | mysqlnd is the default | 
| 5.3.x | libmysqlclient | --with-mysqli=mysqlnd | --with-mysqli=/path/to/mysql_config | mysqlnd is supported | 
| 5.0.x, 5.1.x, 5.2.x | libmysqlclient | Not Available | --with-mysqli=/path/to/mysql_config | mysqlnd is not supported | 
   Note that it is possible to freely mix MySQL extensions and client
   libraries. For example, it is possible to enable the MySQL extension
   to use the MySQL Client Library (libmysqlclient), while configuring the
   mysqli extension to use the MySQL Native Driver.
   However, all permutations of extension and client library are
   possible.
  
On Windows, php_mysqli.dll DLL must be enabled in php.ini.
   As with enabling any PHP extension (such as
   php_mysqli.dll), the PHP directive
   extension_dir should be set
   to the directory where the PHP extensions are located. See also the
   Manual Windows Installation
   Instructions. An example extension_dir
   value is c:\php\ext.
  
Note:
If when starting the web server an error similar to the following occurs:
"Unable to load dynamic library './php_mysqli.dll'", this is because php_mysqli.dll cannot be found by the system.
