customer.module

<?php
/**
 * Implements hook_menu().
 */
function customer_menu() {
	$items['customer/all'] = array(
    'title' => 'Customer Information',
    //'type' => MENU_NORMAL_ITEM,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('customer_phone_unique_autocomplete'),
    'access arguments' => array('view homedeliverys'),
    //'file' => 'ajax_example_autocomplete.inc',
    'weight' => 11,
  );
  $items['customer/all/unique_node_autocomplete_callback'] = array(
    'page callback' => 'customer_phone_unique_node_autocomplete_callback',
    //'file' => 'ajax_example_autocomplete.inc',
    'type' => MENU_CALLBACK,
    'access arguments' => array('view homedeliverys'),
  );
  
  return $items;
}

/**
 * A unique autocomplete form which looks up customer information by phone number in the homedelivery table, but must keep track of the aid, because
 * phone number are certainly not guaranteed to be unique.
 *
 * @param $form
 * @param $form_state
 * @return array
 */
function customer_phone_unique_autocomplete($form, &$form_state) {

  $form['info'] = array(
    '#markup' => '<div>' . t("Enter customer phone number to searching existing customer information.") . '</div>',
  );

  $form['phonenumber'] = array(
    '#type' => 'textfield',
    '#phonenumber' => t('Enter phone number here:'),
    // The autocomplete path is provided in hook_menu in ajax_example.module.
    '#autocomplete_path' => 'customer/all/unique_node_autocomplete_callback',
  );

  $form['actions'] = array(
    '#type' => 'actions'
  );

  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
  );

  return $form;
}

/**
 * Submit handler for node lookup unique autocomplete.
 *
 * This funtion does not work well at this moment, 
 * thus, submitting triggers nothing other than set a message saying phone number is found.
 * @param $form
 * @param $form_state
 */
function customer_phone_unique_autocomplete_submit($form, &$form_state) {
	drupal_set_message(t('Phone number ' . $form_state['values']['phonenumber'] . ' is found.'));
	
	//$phonenumber = homedelivery_load($form_state['values']['phonenumber']);
  //drupal_set_message(t('You found homedelivery with phone number %phonenumber', array('%phonenumber' => $phonenumber->field_cnumber_value)));
}

/**
 * Autocomplete callback for customer information by phone number.
 *
 * @param $string
 *   The string that will be searched.
 */
function customer_phone_unique_node_autocomplete_callback($string = "") {
  $matches = array();
  if ($string) {
    $result = db_select('field_data_field_cnumber')
      ->fields('field_data_field_cnumber', array('entity_id', 'field_cnumber_value'))
      ->condition('field_cnumber_value', db_like($string) . '%', 'LIKE')
      ->range(0, 10)
      ->execute();
    foreach ($result as $phonenumber) {
      $matches[$phonenumber->field_cnumber_value] = check_plain($phonenumber->field_cnumber_value);
    }
  }

  drupal_json_output($matches);
}