What is the best way to override changes to CRM_Core_Config?

Question

What is the best way to override changes to CRM_Core_Config without modifying the original. Have tried through inheritance, but generates the following code:

Fatal error: Cannot redeclare class CRM_Core_Config ....../code/sites/all/civiphp/CRM/Core/Config.php on line 854

It isn't possible to dynamically load and unload the class, so I was thinking of writing a module which modifies the object after it has loaded via a hook. At least this would survive upgrades.

• http://wiki.civicrm.org/confluence/display/CRMDOC/hook_civicrm_config

Answer 1

I've come up with this function to clear cache, when file paths change.

function cacheoff_civicrm_config(&$config) {

  // 1. Get document root from the server
  // 2. Compare to a set path in the cache
  // If 2. doesn't start with 1., then regenerate cache
  // This means the file path has changed

  $templateDir = $config->customTemplateDir;
  $document_root = $_SERVER['DOCUMENT_ROOT'];

  if (!substr($templateDir, 0, strlen($document_root)) === $document_root) {

    CRM_Core_Error::debug( "Path changed: " . $document_root . " doesn't match " . $templateDir ); 
    CRM_Core_Config::clearDBCache();

  }
  _cacheoff_civix_civicrm_config($config);
}

Answer 2

As you have found out, the hook civicrm_config is just the way to do that :-)

Answer 3

Module available: https://github.com/adam-devapp/drupal-pantheon-civicrm-cache-clear/tree/master/civicrm_cache_clear

Needed to be in Drupal, as CiviCRM extensions won't work if the path changes underneath them.