PHP version 7.2 or newer is required, with the *intl* extension and *mbstring* extension installed. These extensions are enabled in php.ini file.
The following PHP extensions should be enabled on your server: php-json, php-mysqlnd, php-xml
To work with CURLRequest, you will need libcurl installed

Supported Databases by CodeIgniter 4:

  • MySQL (5.1+) via the MySQLi driver
  • PostgreSQL via the Postgre driver
  • SQLite3 via the SQLite3 driver

Not all of the drivers have been converted/rewritten for CodeIgniter4:
MySQL (5.1+) ,Oracle, PostgreSQL, MS SQL, sqlsrv, SQLite, CUBRID, Interbase/Firebird, ODBC