Change Default Database connection Dynamically.

laravel-config-database.php

<?php

return [
    //...
    //...
    'default' => 'mysql_primary',
    'connections' => [
        //..
        //Our Default Database Connection
        'mysql_primary' => [
            'driver' => 'mysql',
            'host' => 'localhost',
            'database' => 'my_first_db',
            'username' => 'root',
            'password' => '',
            'charset' => 'utf8',
            'collation' => 'utf8_unicode_ci',
            'prefix' => '',
            'strict' => false,
        ],
        
        //Our Secondary Database Connection
        'mysql_second' => [
            'driver' => 'mysql',
            'host' => 'localhost',
            'database' => 'my_second_db',
            'username' => 'root',
            'password' => '',
            'charset' => 'utf8',
            'collation' => 'utf8_unicode_ci',
            'prefix' => '',
            'strict' => false,
        ],
        //..
        //...
    ],
    //..
    //...
];