Solution to Moodle Error: Coding error detected, it must be fixed by a programmer: Failed to unserialise data from file. Either failed to read, or failed to write.

Did you ever come across the following error when you try to access Moodle,

"Coding error detected, it must be fixed by a programmer: Failed to unserialise data from file. Either failed to read, or failed to write."

This usually happens when cache files are corrupted, one probable cause can be improper shutdown of Moodle system.

Here is the solution to fix the issue.

1. Go to Moodle root directory
    #cd /var/www/html/moodle
  
2. Run the command  
   #php admin/cli/purge_caches.php

3. Go to moodledata/cache directory

  #cd /var/moodledata/cache

  

4. Remove the cache store directory, DO NOT remove of change the core_component.php file

   # rm -rf cachestore_file/

5. Refresh the Moodle Page. Its should work


Source : https://sjamso.blogspot.com/2018/08/solution-to-moodle-error-coding-error.html