get_option return incorrect values

You can just use the get_option() function like this:

<?php

$main_dashboard_check = get_option( 'main_dashboard_check' );
var_dump( $main_dashboard_check ); /* outputs false if the value does not exist */

$main_dashboard_check = get_option( 'main_dashboard_check', 'default_value' );
var_dump( $main_dashboard_check ); /* outputs 'default_value' if the value does not exist */

?>