Allow to query a database

0.4.0 2023-06-22 21:56 UTC

This package is auto-updated.

Last update: 2023-11-02 19:34:57 UTC


This library offers a simple layer of abstraction for database operations.


To get a database instance, you need to pass configuration as an array. The properties and values depend on the engine you want to use.


Key Value
engine MySQLiEngine class reference
host The MySQL hostname, e.g. "localhost"
username The MySQL user to use for connection
password The clear text password to use
database The default db to select for queries (optional)
fetch_mode The default mode to fetch rows MYSQLI_ASSOC

For example:

    'engine' => Keruald\Database\Engines\MySQLiEngine::class,
    'host' => 'localhost',
    'username' => 'app',
    'password' => 'someSecret',
    'database' => 'app',          // optional

About fetch_mode parameter

The fetch_mode parameter is used to determine how to represent results:

  • MYSQLI_ASSOC will use column names
  • MYSQLI_NUM will use an enumerated array (0, 1, 2, …)
  • MYSQLI_BOTH will use both of them

The code offers MYSQLI_ASSOC as default value to allow to directly represent a row result as API output and encourage to take care of the column names for better code maintenance. If you wish to switch to default MySQLi behavior, use MYSQLI_BOTH instead.

Those constants are defined by the MySQLi extension.

Legacy drivers

The mysql extension has been deprecated in PHP 5.7 and removed in PHP 7. As such, this extension isn't supported anymore. You can use straightforwardly replace 'MySQL' by 'MySQLi' as engine.

Specialized drivers for tests


The blackhole engine does nothing and always returns true as query result.

This engine can be used for mocks:

  • directly, when database behavior does not matter
  • to build a mock by overriding behavior of query() or any other method

It can also be used with the loader, without any engine-specific configuration:

    'engine' => Keruald\Database\Engines\BlackholeEngine::class,


The mock database is a simple implementation of the blackhole engine as mocking service to use when you want to return a deterministic response to known queries.

A benefit is you don't need a running database server for your unit tests.

You can pass to the withQueries method an array with one item per query:

  • key: the SQL query
  • value: an array with all rows for that query

For example:

    public function testGetFruits () : void {
        $queries = [
            "SELECT name, color FROM fruits" => [
                [ "name" => "strawberry", "color" => "red" ],
                [ "name" => "blueberry", "color" => "violet" ],

        $db = (new MockDatabaseEngine())

        // Inject $db to a class and test it

To return only one row, you can use [[…]] to represent an array of one array:

        $queries = [
            "SELECT 1+1" => [[ "1+1" => 2 ]],

The queries results are then wrapped in the MockDatabaseResult class.

When the query doesn't exist, an exception is thrown.

We recommend a mixed approach of the Blackhole engine when results don't matter, and of this class when you need some control on it.