code: public function unregister()
      {
          if (!$this->registered) {
              return;
          }
          /*
              set and restore error handler to determine the current error handler
          */
          $errHandlerCur = \set_error_handler(array($this, 'handleError'));
          \restore_error_handler();
          if ($errHandlerCur == array($this, 'handleError')) {
              // we are the current error handler
              \restore_error_handler();
          }
          /*
              set and restore exception handler to determine the current error handler
          */
          $exHandlerCur = \set_exception_handler(array($this, 'handleException'));
          \restore_exception_handler();
          if ($exHandlerCur == array($this, 'handleException')) {
              // we are the current exception handler
              \restore_exception_handler();
          }
          \ini_set('display_errors', $this->prevDisplayErrors);
          $this->prevErrorHandler = null;
          $this->prevExceptionHandler = null;
          $this->registered = false;  // used by $this->onShutdown()
          return;
      }
docs: un-register this error handler and shutdown function
  
  Note:  PHP conspicuously lacks an unregister_shutdown_function function.
  Technically this will still be registered, however:
  $this->registered will be used to keep track of whether
  we're "registered" or not and behave accordingly
  
  @return void