a.php

<?php 

function phpbb_get_max_setting_from_group(\phpbb\db\driver\driver_interface $db, $user_id, $setting)
{
	if ($setting !== 'max_recipients' && $setting !== 'message_limit')
	{
		throw new InvalidArgumentException('Setting "' . $setting . '" is not supported');
	}

	// Get maximum number of allowed recipients
	$sql = 'SELECT MAX(g.group_' . $setting . ') as max_setting
		FROM ' . GROUPS_TABLE . ' g, ' . USER_GROUP_TABLE . ' ug
		WHERE ug.user_id = ' . (int) $user_id . '
			AND ug.user_pending = 0
			AND ug.group_id = g.group_id';
	$result = $db->sql_query($sql);
	$max_setting = (int) $db->sql_fetchfield('max_setting');
	$db->sql_freeresult($result);

	if ($max_setting)
	{
		// If the user is limited by a group, check whether he is also set to
		// unlimited in another group (value 0)
		$sql = 'SELECT g.group_' . $setting . ' as max_setting
			FROM ' . GROUPS_TABLE . ' g, ' . USER_GROUP_TABLE . ' ug
			WHERE ug.user_id = ' . (int) $user_id . '
				AND ug.user_pending = 0
				AND ug.group_id = g.group_id
				AND g.group_max_recipients = 0';
		$result = $db->sql_query($sql);
		$is_unlimited = $db->sql_fetchfield('max_setting');
		$db->sql_freeresult($result);

		$max_setting = ($is_unlimited === false) ? $max_setting : 0;
	}

	return $max_setting;
}