test2

$meta_query = array(
	'relation' => 'AND',
	array(
		'key'     => '$second_str',
		'compare' => 'EXISTS',
	),
	array(
		'key'     => '$second_str',
		'value'   => 'on',
		'compare' => '=',
	),
	array(
		'key'     => '$opening_time_str_2',
		'value'   => '$current_time',
		'compare' => '<=',
	),
	array(
		'key'     => '$closing_time_str_2',
		'value'   => '$current_time',
		'compare' => '>=',
	),
);