\Bitrix\Main\EventManager::getInstance()->addEventHandlerCompatible(
    'main', 'OnEpilog',
    function () {
        ob_start();
        include($_SERVER['DOCUMENT_ROOT'] . '/bitrix/php_interface/include/schema.php');
        $html = ob_get_clean();
        \Bitrix\Main\Page\Asset::getInstance()->addString($html);
    }
);<pre>[RuntimeException] 
Could not start session because headers have already been sent. &quot;/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/php_interface/init.php&quot;:145. (0)
/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/modules/main/lib/session/session.php:143
#0: Bitrix\Main\Session\Session-&gt;start()
	/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/modules/main/lib/session/kernelsessionproxy.php:47
#1: Bitrix\Main\Session\KernelSessionProxy-&gt;start()
	/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/modules/main/include.php:176
#2: require_once(string)
	/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/modules/main/include/prolog_before.php:19
#3: require_once(string)
	/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/modules/main/include/prolog.php:10
#4: require_once(string)
	/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/bitrix/header.php:1
#5: require(string)
	/home/f/f92573hj/bx.f92573hj.beget.tech/public_html/index.php:2
----------
</pre>