Use adapter-approach to allow usage of mysqli, PDO, ...

[k00ni]

It would allow us to avoid breaking changes and opens the door for further adapters.

For now, i would suggest:

• [x] mysqli (default case, to be compatible with 2.3.1 and lower)
  • [x] separate mysqli-functions from ARC2 code. currently ARC2 heavily relies on using a mysqli connection, which makes it impossible to use another backend.
  • take care for MySQL 8.0 problems in test environment moved, maybe later
• [x] PDO (should be default in 3.x or later)

Selected adapter when provide the DB configuration.

for mysqli

In general, you don't have to do anything, because the system uses mysqli adapter as default. But you can be explicit:

$dbConfig = [
    // ...
    'db_adapter' => 'mysqli',
];

for PDO

$dbConfig = [
    // ...
    'db_adapter' => 'pdo',
    'db_pdo_protocol' => 'mysql'
];

[k00ni]

Implemented.