message: Fix typo in documented XDEBUG variable name
diff: @@ -78,4 +78,4 @@ Environment variables are meant to do common behavior changes of php.
  | `PHP_MAX_FILE_UPLOADS` | `20` | The maximum number of files allowed to be uploaded simultaneously, [see php.net](http://php.net/manual/en/ini.core.php#ini.max-file-uploads)|
  | `PHP_MAX_INPUT_VARS` | `2000` | How many input variables will be accepted, [see php.net](http://php.net/manual/en/info.configuration.php#ini.max-input-vars)
  | `PHP_MEMORY_LIMIT` | `400M` | Maximum amount of memory a script may consume, [see php.net](http://php.net/memory-limit) |
  -| `XDEBUG_ENABLED` | (not set) | Used to enable xdebug extension, [see php.net](http://php.net/manual/en/apc.configuration.php#ini.apc.enabled) |
  +| `XDEBUG_ENABLE` | (not set) | Used to enable xdebug extension, [see php.net](http://php.net/manual/en/apc.configuration.php#ini.apc.enabled) |
  