gistfile1.php

<?php
/**
 * Example of placeholder text on a FAPI form element.
 */
$form['contact']['customerfirstname'] = array(
  '#type' => 'textfield',
  '#title' => t('First name'),
  '#required' => TRUE,
  // Other element settings...
  '#attributes' => array(
    'placeholder' => t('Enter your first name'),
  ),
);