Example working Craft Commerce config file for payment details

commerce.php

<?php
// This controls and contains what keys/passwords are used for dev/live environments.

return [
    
    // THIS * ENTRY MUST BE PRESENT - EVEN IF EMPTY!
    '*' => array(
    ),

    // DEV Details - i.e. your Paypal sandbox details for example
    'dev.whatever.net' => array(
 
        'paymentMethodSettings' => [
            //eWay Sandbox
            '1' => [
                'testMode' => true,
                'apiKey' => 'whatever',
                'password' => 'whatever',
                'CSEKey' => 'whatever',

            ],           
            // 2 - MANUAL
            // 3 - DUMMY
            // 4 - Paypal Express
            '4' => [
                'testMode' => true,
                'password' => 'whatever',
                'username' => 'whatever',
                'signature' => 'whatever'
            ],
        ],
    ),

    // PRODUCTION Details - live payment stuff here
    'whatever.com' => array(             
        'paymentMethodSettings' => [
            //eWay LIVE
            '1' => [
                'testMode' => false,
                'apiKey' => 'whatever',
                'password' => 'whatever',
                'CSEKey' => 'whatever',
            ],
            // 2 - MANUAL
            // 3 - DUMMY
            // 4 - Paypal Express
            '4' => [
                'testMode' => false,
                'password' => 'whatever',
                'username' => 'whatever',
                'signature' => 'whatever'
            ],            
        ],        
    ),    
];