< ?php
 	$arUrlRewrite=array (
 		array (
 			'CONDITION' => '#^/([a-zA-Z0-9_-]*)/([a-zA-Z0-9_-]*)/#',
 			'RULE' => "tw=n&folder=$1§=$2&$3",
 			'SORT' => 100,
 			'ID' => '',
 			'PATH' => '/$1/index.php',
 		),
 	);<pre>[RuntimeException] 
Could not start session because headers have already been sent. &quot;/home/s/siteform/siteform.ru/public_html/urlrewrite.php&quot;:1. (0)
/home/s/siteform/siteform.ru/public_html/bitrix/modules/main/lib/session/session.php:141
#0: Bitrix\Main\Session\Session-&gt;start()
	/home/s/siteform/siteform.ru/public_html/bitrix/modules/main/lib/session/kernelsessionproxy.php:42
#1: Bitrix\Main\Session\KernelSessionProxy-&gt;start()
	/home/s/siteform/siteform.ru/public_html/bitrix/modules/main/include.php:169
#2: require_once(string)
	/home/s/siteform/siteform.ru/public_html/bitrix/modules/main/include/prolog_before.php:14
#3: require_once(string)
	/home/s/siteform/siteform.ru/public_html/bitrix/modules/main/include/prolog.php:10
#4: require_once(string)
	/home/s/siteform/siteform.ru/public_html/bitrix/header.php:1
#5: require(string)
	/home/s/siteform/siteform.ru/public_html/404.php:8
#6: include_once(string)
	/home/s/siteform/siteform.ru/public_html/bitrix/urlrewrite.php:4
----------
</pre>