Fatal error: PHP error in file /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/util/StringUtil.class.php (422): Array and string offset access syntax with curly braces is deprecated

Information:

error message: PHP error in file /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/util/StringUtil.class.php (422): Array and string offset access syntax with curly braces is deprecated
error code: 0
file: /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/system/WCF.class.php (255)
php version: 7.4.19
wcf version: 1.0.10 (Horizon)
date: Wed, 12 May 2021 17:56:29 +0000
request: /Forum/index.php?page=User&userID=72551
referer:

Stacktrace:

#0 /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/core.functions.php(29): WCF::handleError()
#1 /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/core.functions.php(29): require_once()
#2 /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/system/cache/CacheHandler.class.php(48): __autoload()
#3 /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/system/WCF.class.php(285): CacheHandler->addResource()
#4 /mnt/web019/a0/34/533934/htdocs/Forum/lib/system/WBBCore.class.php(54): WCF->loadDefaultCacheResources()
#5 /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/system/WCF.class.php(278): WBBCore->loadDefaultCacheResources()
#6 /mnt/web019/a0/34/533934/htdocs/Forum/wcf/lib/system/WCF.class.php(90): WCF->initCache()
#7 /mnt/web019/a0/34/533934/htdocs/Forum/global.php(18): WCF->__construct()
#8 /mnt/web019/a0/34/533934/htdocs/Forum/index.php(7): require_once('/mnt/web019/a0/...')
#9 {main}