Calling PHP and Drupal functions from inside a script

When handling VoipScript parameters, VoIP Drupal processes strings that start with the ^ symbol as expressions to be evaluated. For instance, in the following example,

  // get the report
  $script->addSet('forecast_result', '^_get_forecast(%zip_code)');

  // say the weather report
  $script->addSay('%forecast_result');

The variable forecast_result is set with the result of the function _get_forecast().

The same mechanism can be used to call specialized callback functions to process data collected during call execution:

  $prompt = t("Please record your message after the beep.  When done, press the pound key.");
  $timeout = 5;
  $end_key = '#';
  $script->addRecord($prompt, $timeout, $end_key);

  $script->addSay(t('About to start processing the recorded file.'));
  $script->addSet('callback_result',
    '^_record_callback(%call_id, %recording_url, %recording_duration)');
  $args = array('@result' => '%callback_result');
  $script->addSay(t('The callback returned: @result', $args));