Answers.Body: <p>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.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-09-21T19:01:11.977Z
Answers.LastActivityDate: 2017-09-21T19:01:11.977Z
Answers.UserDisplayName: zpert
Body: <p>I just upgraded from CiviCRM 4.7.10 to <strong>4.7.24</strong> and I followed the steps on the update page <a href="https://wiki.civicrm.org/confluence/display/CRMDOC/Upgrading+CiviCRM+for+WordPress" rel="nofollow noreferrer">here</a>.  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.</p>
  
  <pre><code>[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-&gt;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-&gt;initialize()
  #4 /home/prairie1/public_html/wp-content/plugins/civicrm/civicrm.php(969): CiviCRM_For_WordPress-&gt;add_core_resources(false)
  #5 /home/prairie1/public_html/wp-includes/class-wp-hook.php(298): CiviCRM_For_WordPress-&gt;admin_page_load('')
  #6 /home/prairie1/public_html/wp-includes/class-wp-hook.php(323): WP_Hook-&gt;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
  </code></pre>
  
  <p>I made sure that civicrm.settings.php had the following at the end:</p>
  
  <pre><code>require_once 'CRM/Core/ClassLoader.php';
  CRM_Core_ClassLoader::singleton()-&gt;register();
  </code></pre>
  
  <p>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.</p>
  
  <p>Thanks a lot!</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-09-21T00:34:51.670Z
Comments.Text: I think this is a duplicate of:
  https://civicrm.stackexchange.com/questions/16218/civicrm-fatal-error-uncaught-crm-core-exception-0-found-installation-canary
Comments.UserDisplayName: KarinG - Semper IT
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-09-21T02:54:29.677Z
Comments.Text: Karin, please advise how you think it's a duplicate... They are different error messages given and different files of CiviCRM, so I don't see that they are related.
Comments.UserDisplayName: zpert
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-09-21T03:30:17.657Z
Comments.Text: Sorry about that - I skimmed over it too quickly
Comments.UserDisplayName: KarinG - Semper IT
Tags: <wordpress><upgrade>
Title: PHP Fatal error Class 'CRM_Extension_ClassLoader' not found in civicrm/civicrm/CRM/Extension/System.php:196
ThreadText: # PHP Fatal error Class 'CRM_Extension_ClassLoader' not found in civicrm/civicrm/CRM/Extension/System.php:196
  
  (Asked by: username_0 on 2017-09-20)
  
  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!
  
  **Tags:** wordpress, upgrade
  
  > **Comments:**
  > **username_1**: I think this is a duplicate of: https://civicrm.stackexchange.com/questions/16218/civicrm-fatal-error-uncaught-crm-core-exception-0-found-installation-canary  
  > **username_0**: Karin, please advise how you think it's a duplicate... They are different error messages given and different files of CiviCRM, so I don't see that they are related.  
  > **username_1**: Sorry about that - I skimmed over it too quickly  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_0 on 2017-09-21. Score: 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.
  
  
  ---
  
  