Contact form on a node

Hi!

I need to add a contact form to a certain node types where registered and anonymous users can send a message to the node owner. This is actually a classified ad directory where node owner is a registered user who has placed an ad.

I haven't any coder skills but I've managed to get it working - sort of... Code below generates the contact form nicely and submitting works also ok. Code is placed to Display Suite code field, but I suppose it should work in block too.

The problem is, I have noticed that it interferes core search module. Everytime I try to make a search, it gives me white screen and later some errors. If I disable this code, everything works fine. Here's the error:

Notice: Trying to get property of non-object in eval() (line 6 of /var/aegir/platforms/drupal-7.12/modules/php/php.module(80) : eval()'d code).
Notice: Trying to get property of non-object in eval() (line 8 of /var/aegir/platforms/drupal-7.12/modules/php/php.module(80) : eval()'d code).
Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of /var/aegir/platforms/drupal-7.12/includes/entity.inc).
Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->cacheGet() (line 354 of /var/aegir/platforms/drupal-7.12/includes/entity.inc).
Notice: Trying to get property of non-object in designlasi_contact_personal_form() (line 27 of /var/aegir/platforms/drupal-7.12/modules/php/php.module(80) : eval()'d code).
Notice: Trying to get property of non-object in eval() (line 6 of /var/aegir/platforms/drupal-7.12/modules/php/php.module(80) : eval()'d code).
Notice: Trying to get property of non-object in eval() (line 8 of /var/aegir/platforms/drupal-7.12/modules/php/php.module(80) : eval()'d code).
Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of /var/aegir/platforms/drupal-7.12/includes/entity.inc).
Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->cacheGet() (line 354 of /var/aegir/platforms/drupal-7.12/includes/entity.inc).

I would appreciate help with this one :-)

Here's the code:

<?php
// Get node id
$node = node_load(arg(1));

// Only for certain content types
if (($node->type) == 'buyer' OR 'seller') {

$uid = $node->uid;
$recipient = user_load($uid);

// Load required include
module_load_include("inc", "contact", "contact.pages");

function design_contact_personal_form($form, &$form_state, $recipient) {
  global $user;

  $form = contact_personal_form($form, $form_state, $recipient);

  $node = node_load(arg(1));
  drupal_set_title($node->title);

  $form['name'] = array(
    '#type' => 'textfield',
    '#title' => t('Your name'),
    '#maxlength' => 255,
    '#default_value' => $user->uid ? format_username($user) : '',
    '#required' => TRUE,
    '#size' => 35,
  );

  $form['mail'] = array(
    '#type' => 'textfield',
    '#title' => t('Your e-mail address'),
    '#maxlength' => 255,
    '#default_value' => $user->uid ? $user->mail : '',
    '#required' => TRUE,
    '#size' => 35,
  );

  // Load title
  $form['subject'] = array(
    '#type' => 'textfield',
    '#title' => t('Subject'),
    '#size' => 35,
    '#default_value' => 'Your classified ad',
    '#required' => TRUE,
  );

  $form['message'] = array(
    '#type' => 'textarea',
    '#title' => t('Message'),
    '#required' => TRUE,
    '#rows' => 4,
  );

return($form);
}

function design_contact_personal_form_validate($form, $form_state) {
  return(contact_personal_form_validate($form, $form_state));
}

function design_contact_personal_form_submit($form, $form_state) {
  $form = contact_personal_form_submit($form, $form_state);

  // No redirect
  $form_state['redirect'] = drupal_get_destination();

  return($form);  
}

// Print form
return drupal_render(drupal_get_form('design_contact_personal_form', $recipient)); 

} // End
?>