PHP Fatal error Class 'CRM_Extension_ClassLoader' not found in civicrm/civicrm/CRM/Extension/System.php:196

Question

I just upgraded from CiviCRM 4.7.10 to 4.7.24 and I followed the steps on the update page here. When I copied the new version to the plugins folder, I started receiving this error in the admin portion of WordPress when I tried to load any pages of CiviCRM.

[20-Sep-2017 20:49:48 UTC] PHP Fatal error:  Uncaught Error: Class 'CRM_Extension_ClassLoader' not found in /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm/CRM/Extension/System.php:196
Stack trace:
#0 /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm/Civi/Core/Container.php(395): CRM_Extension_System->getClassLoader()
#1 /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/Config.php(112): Civi\Core\Container::boot(true)
#2 /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm.php(672): CRM_Core_Config::singleton()
#3 /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm.php(1121): CiviCRM_For_WordPress->initialize()
#4 /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm.php(969): CiviCRM_For_WordPress->add_core_resources(false)
#5 /home/prairie1/public_html/wp-includes/class-wp-hook.php(298): CiviCRM_For_WordPress->admin_page_load('')
#6 /home/prairie1/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters('', Array)
#7 /home/prairie1/public_html/wp-includes/plugin.ph in /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm/CRM/Extension/System.php on line 196

I made sure that civicrm.settings.php had the following at the end:

require_once 'CRM/Core/ClassLoader.php';
CRM_Core_ClassLoader::singleton()->register();

I also started off with php version 5.5 running, but I read that I could try 7 and it was supported, so I switched. It gave me the stack trace where 5.5 did not, but didn't help the error.

Thanks a lot!

Answer 1

Sorry, I finally found the solution. It was incredibly simple but hard to find. When I uploaded the new version of civicrm using FileZilla, it said all transfers were successful and 0 failed. However, there were a few files, one being ClassLoader.php, that were 0 in File Size. It marked it as successfully uploaded, but didn't upload any content. I just used FileZilla to upload all files again with the option to only Overwrite if the size was different, and it fixed these errors.