Thank you, I removed the folder and now website is working, but how can I add Webfeed to the plugins?
because It’s essential for the JournalTOCs indexing.
I think the problem has been caused with incompatible plugin version. Which version of the OJS are you using? Or, maybe: do you have the old version of the plugin somewhere?
Actually I could not find a .ta.gz file for weebFeed, I made it by folder and I tried to upgrade, there was error, so I manually removed the current webFeed folder and replaced it with new webFeed folder and the problem occurred.
So I would like to know, now how can I have this plugin running in my website?
getTemplateVars() was introduced only in Smarty v3, but latest stable release is still using Smarty 2. You have downloaded updated version of the plugin for the OJS version that it wan’t released yet. Webfeed plugin is shipped with the OJS release, so you can just download the one that corresponds with your version and copy it to your relevant directory
You may also need to check the permissions for copied files. They should be readable by the group that includes your webserver (if Apache, on Ubuntu it is usually called www-data).