function llms_is_post_restricted_by_membership( $post_id, $user_id = null ) {

	// don't check these posts types.
	$skip = apply_filters(
		'llms_is_post_restricted_by_membership_skip_post_types',
		array(
			'course',
			'lesson',
			'llms_quiz',
			'llms_membership',
			'llms_question',
			'llms_certificate',
			'llms_my_certificate',
		)
	);

	if ( in_array( get_post_type( $post_id ), $skip, true ) ) {
		return false;
	}

	$memberships = get_post_meta( $post_id, '_llms_restricted_levels', true );
	$restricted  = get_post_meta( $post_id, '_llms_is_restricted', true );

	if ( 'yes' === $restricted && $memberships && is_array( $memberships ) ) {

		// if no user, return the first membership from the array as the restriction id.
		if ( ! $user_id ) {

			$restriction_id = array_shift( $memberships );

		} else {

			$student = llms_get_student( $user_id );
			if ( ! $student ) {

				$restriction_id = array_shift( $memberships );

			} else {

				// reverse so to ensure that if user is in none of the memberships,
				// they'd encounter the same restriction settings as a visitor.
				$memberships = array_reverse( $memberships );

				// loop through the memberships.
				foreach ( $memberships as $mid ) {

					// set this as the restriction id.
					$restriction_id = $mid;

					// once we find the student has access break the loop,
					// this will be the restriction that the template loader will check against later.
					if ( $student->is_enrolled( $mid ) ) {
						break;
					}
				}
			}
		}

		return absint( $restriction_id );

	}

	return false;

}