undefined function mb_substr(): what to do when you get this error ?

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Problem

When installing combostrap on the server, the below error may occurs. 

[Sat Jan 29 15:27:04.904342 2022] [php7:error] [pid 68063] [client 127.0.0.1:58960] PHP Fatal error:  Uncaught Error: Call to undefined function mb_substr() in /var/www/html/dokuwiki/lib/plugins/combo/ComboStrap/DokuPath.php:167
Stack trace:
  /var/www/html/dokuwiki/lib/plugins/combo/ComboStrap/DokuPath.php(226): ComboStrap\\DokuPath->__construct()
  /var/www/html/dokuwiki/lib/plugins/combo/ComboStrap/Page.php(247): ComboStrap\\DokuPath::createPagePathFromPath()
  /var/www/html/dokuwiki/lib/plugins/combo/ComboStrap/Page.php(271): ComboStrap\\Page->__construct()
  /var/www/html/dokuwiki/lib/plugins/combo/action/metalang.php(41): ComboStrap\\Page::createPageFromId()
  /var/www/html/dokuwiki/inc/Extension/EventHandler.php(81): action_plugin_combo_metalang->load_lang()
  /var/www/html/dokuwiki/inc/Extension/Event.php(72): dokuwiki\\Extension\\EventHandler->process_event()
  /var/www/html/dokuwiki/inc/Extension/Event.php(128): dokuwiki\\Extension\\Event->advise_before()
  /var/www/html/dokuwiki/inc/Extension/Event.php(195): dokuwiki\\Extension\\Event->trigger()
  /var/www/html/dokuwiki/inc/init.php(224): dokuwiki\\E in /var/www/html/dokuwiki/lib/plugins/combo/ComboStrap/DokuPath.php on line 167, referer: http://localhost/doku.php?id=start&do=admin&page=extension

Solution

The mb_substr function is part of the mbstring extension and should be installed.

This extension is installed on all hosted php server. If you are installing yourself your server, you should install all the extensions listed in the requirement page.

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