Joomla-cms: Update PHP to 7.1 / 7.2 creates "Fatal Error 0 Using $this when not in object context"

[solenthaler]

Steps to reproduce the issue

Update a Joomla 8.10.3 Installation from PHP 7.0 to 7.1 or 7.2
Starting the Website

Expected result

Normal Operation:

Actual result

Withe Page with
--> Fatal Error 0 Using $this when not in object context

System information (as much as possible)

Call stack

Function Location
1 ()JROOT/libraries/src/Application/CMSApplication.php:369
2 Joomla\CMS\Application\CMSApplication::getMenu() JROOT/libraries/src/Application/SiteApplication.php:275
3 Joomla\CMS\Application\SiteApplication::getMenu() JROOT/templates/aerzte_theme517/index.php:209
4 require() JROOT/libraries/src/Document/HtmlDocument.php:658
5 Joomla\CMS\Document\HtmlDocument->_loadTemplate() JROOT/libraries/src/Document/HtmlDocument.php:720
6 Joomla\CMS\Document\HtmlDocument->_fetchTemplate() JROOT/libraries/src/Document/HtmlDocument.php:535
7 Joomla\CMS\Document\HtmlDocument->parse() JROOT/libraries/src/Application/CMSApplication.php:1027
8 Joomla\CMS\Application\CMSApplication->render() JROOT/libraries/src/Application/SiteApplication.php:780
9 Joomla\CMS\Application\SiteApplication->render() JROOT/libraries/src/Application/CMSApplication.php:201
10 Joomla\CMS\Application\CMSApplication->execute() JROOT/index.php:49

Additional comments

[mbabker]

Unfortunately this is an error in your template JROOT/templates/aerzte_theme517/index.php:209. Basically, it's doing something like JSite::getMenu() or Joomla\CMS\Application\SiteApplication::getMenu() which calls the getMenu method in a static context, which is the incorrect way of calling that method. The code should be JFactory::getApplication()->getMenu().

[davietechfl]

Thank you, just worked for me on a Joomla site, changed the file as specified and site returned to normal opeation on PHP 7.1. Joomla recommended the update but without your change to the index.php site would not display, much appreciated.

[Real-Integrated]

@mbabker I realize this is old and closed... but you just saved me a monumental amount of time. Thank you very much.

[Tanyansp]

Подскажите, у меня такая же проблема, но такого кода в index нет. Как решить? ошибка: Error: Call to undefined method Error::get(): Using $this when not in object context