Error Function - CiviCRM Documentation

Fatal error: require_once() [function.require]: Failed opening required 'CRM/Core/Config.php' (include_path='.:/usr/local/lib/php') in /home/xxx/modules/civicrm/drupal/civicrm.module on line 215

This error indicates that the path to CiviCRM files is not being set, or is being set incorrectly. A further symptom can be seen in the second part of the error message, which shows the current path info. You should always see the word 'civicrm' in the include path. Note in the example below that this is missing...

 Fatal error: require_once() \[function.require\]: Failed opening required 
 'CRM/Core/Config.php' (include_path='.:/usr/local/lib/php') in  
 /home/xxx/modules/civicrm/drupal/civicrm.module on line 215

For Drupal installations, follow these steps to resolve the problem. These instructions are for Drupal 4.7 and CiviCRM 1.5.

Make sure you've downloaded the latest CiviCRM 1.5 tarball from our downloads site.
If you've installed any prior version of CiviCRM - make sure that you've removed ALL DIRECTORIES AND FILES from that prior version. Files from any prior versions (especially civicrm.module) located anywhere below your Drupal modules directory will cause unknown/fatal errors. For example, renaming the directory containing an older version as /civicrm.bak/ - and leaving it below the modules directory - will cause problems.
Make sure that your current settings file - civicrm.settings.php - is located in [drupal_rooot]/sites/default directory
If this is an upgrade from a prior version - rename your existing settings file to civicrm.settings.php.bak and copy the sample settings file from modules/civicrm/civicrm.settings.php.sample to sites/default/civicrm.settings.php.
Then merge values from the prior settings file (.bak) into the the new file and modify any new settings using the inline instructions in the file.
All file system paths should be entered as ABSOLUTE paths. Do not use RELATIVE paths.
Verify that you are not running an incompatible version of Zend Optimizer (2.5.7). See [this page ] for more info.
Now verify that the file you are editing is the one being invoked by adding the following lines to the top of the file - just below the opening <?php tag:
```
      echo "In civicrm.settings.php";
      exit();
```
Now try to load a CiviCRM page again — you should see the echoed text. If so, remove the lines again from the settings file and, if your $civicrm_root path is set properly, the errors should be resolved.