Php/docs/migration5.databases
Databases
There were some changes in PHP 5 regarding databases (MySQL and SQLite).
In PHP 5 the MySQL client libraries are not bundled, because of license
and maintenance problems. MySQL is supported with the only
change being that MySQL support is no longer enabled by
default in PHP 5. This essentially means that
PHP doesn't include the --with-mysql
option in the configure line so
that you must now manually do this when compiling PHP. Windows users will
need to edit php.ini
and enable the php_mysql.dll
DLL as in PHP 4 no such DLL existed, it was simply built into your Windows
PHP binaries.
There is also a new extension, MySQLi (Improved MySQL), which is designed to work with MySQL 4.1 and above.
Since PHP 5, the SQLite extension is built-in PHP. SQLite is an embeddable SQL database engine and is not a client library used to connect to a big database server (like MySQL or PostgreSQL). The SQLite library reads and writes directly to and from the database files on disk.