Help sending specific fields' values to external url from Drupal webform

I have the following codes in webform remote post module, but instead of sending the whole webform fields as it is being done in the module, I need to send data from the fields only present in a custom mysql table on my server. How can I do so?

This is original code from the module:

$component_map = array();
foreach ($node->webform['components'] as $component) {$component_map[$component['cid']] = $component;
}

$payload = array();
foreach ($submission->data as $cid => $component_data) {
    $payload[$component_map[$cid]['form_key']] = implode(', ', $component_data);
}