Fatal error: PHP error in file /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/lib/page/IrcChatPage.class.php (38): Function ereg_replace() is deprecated

Information:

error message: PHP error in file /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/lib/page/IrcChatPage.class.php (38): Function ereg_replace() is deprecated
error code: 0
file: /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/wcf/lib/system/WCF.class.php (255)
php version: 5.5.38
wcf version: 1.0.11 pl 3 (Horizon)
date: Sat, 20 Oct 2018 08:32:19 +0000
request: /index.php?page=IrcChat&s=bc98e6c53c67255a0881d8c2f55c2ee57755f635
referer:

Stacktrace:

#0 [internal function]: WCF::handleError(8192, 'Function ereg_r...', '/var/www/vhosts...', 38, Array)
#1 /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/lib/page/IrcChatPage.class.php(38): ereg_replace()
#2 /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/wcf/lib/page/AbstractPage.class.php(36): IrcChatPage->show()
#3 /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/wcf/lib/util/RequestHandler.class.php(63): AbstractPage->__construct()
#4 /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/wcf/lib/util/RequestHandler.class.php(91): RequestHandler->__construct('IrcChat', Array, 'page')
#5 /var/www/vhosts/ratsclanseite.de/subdomains/wbb/httpdocs/index.php(8): RequestHandler::handle(Array)
#6 {main}