[RuntimeException] 
Could not start session because headers have already been sent. "/home/bitrix/ext_www/mit-group.pl/index.php":2. (0)
/home/bitrix/ext_www/mitgroup.ru/bitrix/modules/main/lib/session/session.php:151
#0: Bitrix\Main\Session\Session->start()
	/home/bitrix/ext_www/mitgroup.ru/bitrix/modules/main/lib/session/kernelsessionproxy.php:47
#1: Bitrix\Main\Session\KernelSessionProxy->start()
	/home/bitrix/ext_www/mitgroup.ru/bitrix/modules/main/include.php:159
#2: require_once(string)
	/home/bitrix/ext_www/mitgroup.ru/bitrix/modules/main/include/prolog_before.php:14
#3: require_once(string)
	/home/bitrix/ext_www/mitgroup.ru/bitrix/modules/main/include/prolog.php:10
#4: require_once(string)
	/home/bitrix/ext_www/mitgroup.ru/bitrix/header.php:1
#5: require(string)
	/home/bitrix/ext_www/mit-group.pl/index.php:2
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