[RuntimeException] 
Could not start session because headers have already been sent. "/home/i/igcmar5b/igc-market.ru/public_html/ajax/marketing.php":2. (0)
/home/i/igcmar5b/igc-market.ru/public_html/bitrix/modules/main/lib/session/session.php:124
#0: Bitrix\Main\Session\Session->start()
	/home/i/igcmar5b/igc-market.ru/public_html/bitrix/modules/main/lib/session/kernelsessionproxy.php:52
#1: Bitrix\Main\Session\KernelSessionProxy->start()
	/home/i/igcmar5b/igc-market.ru/public_html/bitrix/modules/main/include.php:299
#2: require_once(string)
	/home/i/igcmar5b/igc-market.ru/public_html/bitrix/modules/main/include/prolog_before.php:14
#3: require(string)
	/home/i/igcmar5b/igc-market.ru/public_html/ajax/marketing.php:3