use Bitrix\Main\Page\Asset;
Asset::getInstance()->addString('<meta http-equiv="refresh" content="0; url=/index.php/" />', true);

<pre>[RuntimeException] 
Could not start session because headers have already been sent. &quot;/home/h202459050/h202459050.nichost.ru/docs/payplan.php&quot;:1. (0)
/home/h202459050/h202459050.nichost.ru/docs/bitrix/modules/main/lib/session/session.php:143
#0: Bitrix\Main\Session\Session-&gt;start()
	/home/h202459050/h202459050.nichost.ru/docs/bitrix/modules/main/lib/session/kernelsessionproxy.php:47
#1: Bitrix\Main\Session\KernelSessionProxy-&gt;start()
	/home/h202459050/h202459050.nichost.ru/docs/bitrix/modules/main/include.php:182
#2: require_once(string)
	/home/h202459050/h202459050.nichost.ru/docs/bitrix/modules/main/include/prolog_before.php:19
#3: require_once(string)
	/home/h202459050/h202459050.nichost.ru/docs/bitrix/modules/main/include/prolog.php:10
#4: require_once(string)
	/home/h202459050/h202459050.nichost.ru/docs/bitrix/header.php:1
#5: require(string)
	/home/h202459050/h202459050.nichost.ru/docs/payplan.php:5
----------
</pre>