[RuntimeException] 
Could not start session because headers have already been sent. "/home/euromulcha/euromulcha.ru/docs/callback/index.php":1. (0)
/home/euromulcha/euromulcha.ru/docs/bitrix/modules/main/lib/session/session.php:151
#0: Bitrix\Main\Session\Session->start()
	/home/euromulcha/euromulcha.ru/docs/bitrix/modules/main/lib/session/kernelsessionproxy.php:47
#1: Bitrix\Main\Session\KernelSessionProxy->start()
	/home/euromulcha/euromulcha.ru/docs/bitrix/modules/main/include.php:180
#2: require_once(string)
	/home/euromulcha/euromulcha.ru/docs/bitrix/modules/main/include/prolog_before.php:19
#3: require(string)
	/home/euromulcha/euromulcha.ru/docs/callback/index.php:3
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