This guide gives you a big picture overview of Drupal concepts, helping you to understand the framework behind Drupal.

System requirements

Detailed system requirements for a Drupal 7 installation.

Installing Drupal 7

How to install Drupal 7.

Updating Drupal 7

How to update your Drupal 7 site

Administering Drupal 7 site

Administering Drupal 7 site

Contributed modules

Documentation for contributed modules for Drupal 7.

Theming Drupal 7

Theming guide for Drupal 7.

Extending Drupal 7

Extend your Drupal 7 site's functionality with contributed modules, or alter its appearance with contributed themes.

Multilingual guide

Multilingual guide for Drupal 7.

Multisite Drupal 7

Drupal can serve many sites from a single codebase.

Choosing a Drupal version

This guide explains Drupal’s version numbering scheme for both Drupal core and contributed modules.

Upgrade to Drupal 7

Upgrade to Drupal 7 from previous major versions of Drupal.

Setting up cron

Setting up cron for Drupal 7

Configuring clean URLs

The guidelines for clean URLs

Migrating to Drupal 7

Migrating to Drupal

Security in Drupal 7

Securing Drupal 7 site

Backing up and migrating a site

Backing up and migrating a site (for example, from one host to another).

Managing site performance and scalability

Managing site performance requires a mix of code optimisation, configuration, and server tuning.

Managing users

How to add and remove Drupal users and manage other user related functionality like roles, permissions, and fields.

Monitoring a site

Monitoring a site

Nodes, content types and fields

Nodes, content types and fields

Organizing content with taxonomy

Organizing content with taxonomy

Site building best practices

Site building best practices

Accessibility

Accessibility tools and best practices

Guidelines for SQL

These guidelines provide some tips for writing efficient SQL code. Guidelines apply to MySQL and PostgreSQL.

This example Drupal source code file (uc_cart_checkout_pane.inc) is included in the DevDaily.com "Drupal Source Code Warehouse" project. The intent of this project is to help you "Learn Drupal by Example".

The uc_cart_checkout_pane.inc Drupal example source code

• @file
• This file contains the callbacks for the default checkout panes supplied with
• Ubercart and their corresponding helper functions. *
• Checkout panes are defined using hook_uc_checkout_pane() and use a callback
• to handle the different processes involved in completing the checkout form.
• The default checkout panes are defined in uc_cart_uc_checkout_pane() in
• uc_cart.module. / /*
• Displays the cart contents for review during checkout. / function uc_checkout_pane_cart($op, $order, $form = NULL, &$form_state = NULL) { switch ($op) {

  case 'view':
    $order->products = uc_cart_get_contents();
    $contents['cart_review_table'] = array(
      '
  

  # theme' => 'uc_cart_review_table',

      '
  

  # items' => $order->products,

      '
  

  # weight' => variable_get('uc_pane_cart_field_cart_weight', 2),

    );
    return array('contents' => $contents, 'next-button' => FALSE);
  case 'review':
    $items = uc_cart_get_contents();
    $output = '';
    foreach ($items as $item) {
      $desc = check_plain($item->title) . uc_product_get_description($item);
      $output .= '';
    }
    $output .= '
  ' . $item->qty . '×
  ' . $desc
                . '
  ' . theme('uc_price', array('price' => $item->price  $item->qty)) . '
  ';
    $review[] = $output;
    return $review;
  

  } } /
• Gets the user's email address for login. /

  function uc_checkout_pane_customer($op, $order, $form = NULL, &$form_state = NULL) { global $user; switch ($op) {

  case 'view':
    if (!empty($order->primary_email)) {
      $email = $order->primary_email;
    }
    elseif (isset($user->mail)) {
      $email = $user->mail;
    }
    else {
      $email = '';
    }
    if ($user->uid) {
      $description = t('Order information will be sent to your account e-mail listed below.');// . '
  '
      $contents['primary_email'] = array('
  

  # type' => 'hidden', '

  value' => check_plain($email));

      $contents['email_text'] = array(
        '
  

  # markup' => '

  ' . t('E-mail address: @email (edit)', array('@email' => $email, '!url' => url('user/' . $user->uid . '/edit', array('query' => drupal_get_destination())))) . '

  ',

      );
    }
    else {
      $description = t('Enter a valid email address for this order or click here to login with an existing account and return to checkout.', array('!url' => url('user/login', array('query' => drupal_get_destination()))));
      $contents['primary_email'] = uc_textfield(t('E-mail address'), $email, TRUE, NULL, 64);
    }
    if (variable_get('uc_cart_email_validation', FALSE) && !$user->uid) {
      $contents['primary_email_confirm'] = uc_textfield(t('Confirm e-mail address'), $_SESSION['email_match'] === FALSE ? '' : $email, TRUE, NULL, 64);
      if ($_SESSION['email_match'] === FALSE) {
        unset($_SESSION['email_match']);
      }
    }
    if ($user->uid == 0) {
      $contents['new_account'] = array();
      if (variable_get('uc_cart_new_account_name', FALSE)) {
        $contents['new_account']['name'] = array(
          '
  

  # type' => 'textfield',

          '
  

  # title' => t('Username'),

          '
  

  # default_value' => $order->data['new_user']['name'],

          '
  

  # maxlength' => 60,

          '
  

  # size' => 32,

        );
      }
      if (variable_get('uc_cart_new_account_password', FALSE)) {
        $contents['new_account']['pass'] = array(
          '
  

  # type' => 'password',

          '
  

  # title' => t('Password'),

          '
  

  # maxlength' => 32,

          '
  

  # size' => 32,

        );
        $contents['new_account']['pass_confirm'] = array(
          '
  

  # type' => 'password',

          '
  

  # title' => t('Confirm password'),

          '
  

  # description' => t('Passwords must match to proceed.'),

          '
  

  # maxlength' => 32,

          '
  

  # size' => 32,

        );
      }
      if (!empty($contents['new_account'])) {
        $array = array(
          '
  

  # type' => 'fieldset',

          '
  

  # title' => t('New account details'),

          '
  

  # description' => variable_get('uc_cart_new_account_details', t('Optional. New customers may supply custom account details.
  We will create these for you if no values are entered.')),

          '
  

  # collapsible' => FALSE,

        );
        $contents['new_account'] = array_merge($array, $contents['new_account']);
      }
      /*
  

  • This code adds profile fields required for registration to the
  • customer checkout pane. However, I don't have the time to fool with
  • validation/submission stuff, so I'm postponing this feature. -RS

        $null = NULL;
        $extra = _user_forms($null, NULL, NULL, 'register');
        if (!empty($extra)) {
          $contents = array_merge($contents, $extra);
        }/
      }
      return array('description' => $description, 'contents' => $contents);
    case 'process':
      $pane = $form_state['values']['panes']['customer'];
      if (!empty($pane['primary_email']) && !valid_email_address($pane['primary_email'])) {
        form_set_error('panes][customer][primary_email', t('You must enter a valid e-mail address.'));
      }
      $order->primary_email = $pane['primary_email'];
      if (variable_get('uc_cart_email_validation', FALSE) && !$user->uid &&
          $pane['primary_email'] !== $pane['primary_email_confirm']) {
        form_set_error('panes][customer][primary_email_confirm', t('The e-mail address did not match.'));
        $_SESSION['email_match'] = FALSE;
      }
      // Invalidate if an account already exists for this e-mail address, and the user is not logged into that account
      if ($user->uid == 0 && !empty($pane['primary_email'])) {
        if (db_query("SELECT uid FROM {users} WHERE mail LIKE :mail", array(':mail' => $pane['primary_email']))->fetchField() > 0) {
          form_set_error('panes][customer][primary_email', t('An account already exists for your e-mail address. You will either need to login with with this e-mail address or use a different e-mail address.'));
        }
      }
      // If new users can specify names or passwords then...
      if ((variable_get('uc_cart_new_account_name', FALSE) ||
          variable_get('uc_cart_new_account_password', FALSE)) &&
          $user->uid == 0) {
        // Validate the username.
        if (variable_get('uc_cart_new_account_name', FALSE) && !empty($pane['new_account']['name'])) {
          $message = user_validate_name($pane['new_account']['name']);
          if (!empty($message)) {
            form_set_error('panes][customer][new_account][name', $message);
          }
          if (db_query("SELECT uid FROM {users} WHERE name LIKE :name", array(':name' => $pane['new_account']['name']))->fetchField()) {
            form_set_error('panes][customer][new_account][name', t('The username %name is already taken. Please enter a different name or leave the field blank for your username to be your e-mail address.', array('%name' => $pane['new_account']['name'])));
          }
          $order->data['new_user']['name'] = $pane['new_account']['name'];
        }
        // Validate the password.
        if (variable_get('uc_cart_new_account_password', FALSE)) {
          if (strcmp($pane['new_account']['pass'], $pane['new_account']['pass_confirm'])) {
            form_set_error('panes][customer][new_account][pass_confirm', t('The passwords you entered did not match. Please try again.'));
          }
          $order->data['new_user']['pass'] = $pane['new_account']['pass'];
        }
      }
      if ($user->uid) {
        $order->uid = $user->uid;
      }
      return TRUE;
    case 'review':
      $review[] = array('title' => t('E-mail'), 'data' => check_plain($order->primary_email));
      return $review;
    case 'settings':
      $form['uc_cart_email_validation'] = array(
        '
    

    # type' => 'checkbox',

        '
    

    # title' => t('Require e-mail confirmation in checkout for anonymous customers.'),

        '
    

    # default_value' => variable_get('uc_cart_email_validation', FALSE),

      );
      $form['uc_cart_new_account_name'] = array(
        '
    

    # type' => 'checkbox',

        '
    

    # title' => t('Allow anonymous customers to specify a new user account name.'),

        '
    

    # default_value' => variable_get('uc_cart_new_account_name', FALSE),

      );
      $form['uc_cart_new_account_password'] = array(
        '
    

    # type' => 'checkbox',

        '
    

    # title' => t('Allow anonymous customers to specify a new user account password.'),

        '
    

    # default_value' => variable_get('uc_cart_new_account_password', FALSE),

      );
      $form['uc_cart_new_account_details'] = array(
        '
    

    # type' => 'textarea',

        '
    

    # title' => t('New account details help message'),

        '
    

    # description' => t('Enter the help message displayed in the new account details fieldset when shown.'),

        '
    

    # default_value' => variable_get('uc_cart_new_account_details', t('Optional. New customers may supply custom account details.
    We will create these for you if no values are entered.')),

      );
      return $form;
    

    }

  } /*

case 'view':
  $description = t('Enter your delivery address and information here.');
  if ((uc_cart_is_shippable() || !variable_get('uc_cart_delivery_not_shippable', TRUE)) &&
       uc_checkout_pane_data('billing', 'weight') < _uc_checkout_pane_data('delivery', 'weight') &&
       _uc_checkout_pane_data('billing', 'enabled')) {
    $contents['copy_address'] = array(
      '

      '

      '

    );
  }
  if ($user->uid) {
    $addresses = uc_select_address($user->uid, 'delivery', 'apply_address(\'delivery\', this.value);', t('Saved addresses'), TRUE);
    if (!empty($addresses)) {
      $contents['delivery_address_select'] = $addresses;
    }
  }
  if (uc_address_field_enabled('first_name')) {
    $delivery_first_name = $order ? $order->delivery_first_name : '';
    $contents['delivery_first_name'] = uc_textfield(uc_get_field_name('first_name'), $delivery_first_name, uc_address_field_required('first_name'));
  }
  if (uc_address_field_enabled('last_name')) {
    $delivery_last_name = $order ? $order->delivery_last_name : '';
    $contents['delivery_last_name'] = uc_textfield(uc_get_field_name('last_name'), $delivery_last_name, uc_address_field_required('last_name'));
  }
  if (uc_address_field_enabled('company')) {
    $delivery_company = $order ? $order->delivery_company : '';
    $contents['delivery_company'] = uc_textfield(uc_get_field_name('company'), $delivery_company, uc_address_field_required('company'), NULL, 64);
  }
  if (uc_address_field_enabled('street1')) {
    $delivery_street1 = $order ? $order->delivery_street1 : '';
    $contents['delivery_street1'] = uc_textfield(uc_get_field_name('street1'), $delivery_street1, uc_address_field_required('street1'), NULL, 64);
  }
  if (uc_address_field_enabled('street2')) {
    $delivery_street2 = $order ? $order->delivery_street2 : '';
    $contents['delivery_street2'] = uc_textfield(uc_get_field_name('street2'), $delivery_street2, uc_address_field_required('street2'), NULL, 64);
  }
  if (uc_address_field_enabled('city')) {
    $delivery_city = $order ? $order->delivery_city : '';
    $contents['delivery_city'] = uc_textfield(uc_get_field_name('city'), $delivery_city, uc_address_field_required('city'));
  }
  if (uc_address_field_enabled('country')) {
    $delivery_country = $order ? $order->delivery_country : NULL;
    $contents['delivery_country'] = uc_country_select(uc_get_field_name('country'), $delivery_country, NULL, 'name', uc_address_field_required('country'));
  }
  if (uc_address_field_enabled('zone')) {
    if (isset($_POST['panes']['delivery']['delivery_country'])) {
      $country_id = intval($_POST['panes']['delivery']['delivery_country']);
    }
    else {
      $country_id = $delivery_country;
    }
    $delivery_zone = $order ? $order->delivery_zone : NULL;
    $contents['delivery_zone'] = uc_zone_select(uc_get_field_name('zone'), $delivery_zone, NULL, $country_id, 'name', uc_address_field_required('zone'));
    if (isset($_POST['panes']) && count($contents['delivery_zone']['

      $contents['delivery_zone']['

    }
  }
  if (uc_address_field_enabled('postal_code')) {
    $delivery_postal_code = $order ? $order->delivery_postal_code : '';
    $contents['delivery_postal_code'] = uc_textfield(uc_get_field_name('postal_code'), $delivery_postal_code, uc_address_field_required('postal_code'), NULL, 10, 10);
  }
  if (uc_address_field_enabled('phone')) {
    $delivery_phone = $order ? $order->delivery_phone : '';
    $contents['delivery_phone'] = uc_textfield(uc_get_field_name('phone'), $delivery_phone, uc_address_field_required('phone'), NULL, 32, 16);
  }
  return array('description' => $description, 'contents' => $contents, 'theme' => 'uc_address_pane');
case 'process':
  foreach (uc_address_field_enabled() as $field) {
    $field = 'delivery' . $field;
    $order->$field = $form_state['values']['panes']['delivery'][$field];
  }
  return TRUE;
case 'review':
  $review[] = array('title' => t('Address'), 'data' => uc_order_address($order, 'delivery', FALSE));
  if (uc_address_field_enabled('phone') && !empty($order->delivery_phone)) {
    $review[] = array('title' => t('Phone'), 'data' => check_plain($order->delivery_phone));
  }
  return $review;

case 'view':
  $description = t('Enter your billing address and information here.');
  if ((uc_cart_is_shippable() || !variable_get('uc_cart_delivery_not_shippable', TRUE)) &&
       uc_checkout_pane_data('delivery', 'weight') < _uc_checkout_pane_data('billing', 'weight') &&
       _uc_checkout_pane_data('delivery', 'enabled')) {
    $contents['copy_address'] = array(
      '

      '

      '

    );
  }
  if ($user->uid) {
    $addresses = uc_select_address($user->uid, 'billing', 'apply_address(\'billing\', this.value);', t('Saved addresses'), TRUE);
    if (!empty($addresses)) {
      $contents['billing_address_select'] = $addresses;
    }
  }
  if (uc_address_field_enabled('first_name')) {
    $billing_first_name = $order ? $order->billing_first_name : '';
    $contents['billing_first_name'] = uc_textfield(uc_get_field_name('first_name'), $billing_first_name, uc_address_field_required('first_name'));
  }
  if (uc_address_field_enabled('last_name')) {
    $billing_last_name = $order ? $order->billing_last_name : '';
    $contents['billing_last_name'] = uc_textfield(uc_get_field_name('last_name'), $billing_last_name, uc_address_field_required('last_name'));
  }
  if (uc_address_field_enabled('company')) {
    $billing_company = $order ? $order->billing_company : '';
    $contents['billing_company'] = uc_textfield(uc_get_field_name('company'), $billing_company, uc_address_field_required('company'), NULL, 64);
  }
  if (uc_address_field_enabled('street1')) {
    $billing_street1 = $order ? $order->billing_street1 : '';
    $contents['billing_street1'] = uc_textfield(uc_get_field_name('street1'), $billing_street1, uc_address_field_required('street1'), NULL, 64);
  }
  if (uc_address_field_enabled('street2')) {
    $billing_street2 = $order ? $order->billing_street2 : '';
    $contents['billing_street2'] = uc_textfield(uc_get_field_name('street2'), $billing_street2, uc_address_field_required('street2'), NULL, 64);
  }
  if (uc_address_field_enabled('city')) {
    $billing_city = $order ? $order->billing_city : '';
    $contents['billing_city'] = uc_textfield(uc_get_field_name('city'), $billing_city, uc_address_field_required('city'));
  }
  if (uc_address_field_enabled('country')) {
    $billing_country = $order ? $order->billing_country : NULL;
    $contents['billing_country'] = uc_country_select(uc_get_field_name('country'), $billing_country, NULL, 'name', uc_address_field_required('country'));
  }
  if (uc_address_field_enabled('zone')) {
    if (isset($_POST['panes']['billing']['billing_country'])) {
      $country_id = intval($_POST['panes']['billing']['billing_country']);
    }
    else {
      $country_id = $billing_country;
    }
    $billing_zone = $order ? $order->billing_zone : NULL;
    $contents['billing_zone'] = uc_zone_select(uc_get_field_name('zone'), $billing_zone, NULL, $country_id, 'name', uc_address_field_required('zone'));
    if (isset($_POST['panes']) && count($contents['billing_zone']['

      $contents['billing_zone']['

    }
  }
  if (uc_address_field_enabled('postal_code')) {
    $billing_postal_code = $order ? $order->billing_postal_code : '';
    $contents['billing_postal_code'] = uc_textfield(uc_get_field_name('postal_code'), $billing_postal_code, uc_address_field_required('postal_code'), NULL, 10, 10);
  }
  if (uc_address_field_enabled('phone')) {
    $billing_phone = $order ? $order->billing_phone : '';
    $contents['billing_phone'] = uc_textfield(uc_get_field_name('phone'), $billing_phone, uc_address_field_required('phone'), NULL, 32, 16);
  }
  return array('description' => $description, 'contents' => $contents, 'theme' => 'uc_address_pane');
case 'process':
  foreach (uc_address_field_enabled() as $field) {
    $field = 'billing' . $field;
    $order->$field = $form_state['values']['panes']['billing'][$field];
  }
  return TRUE;
case 'review':
  $review[] = array('title' => t('Address'), 'data' => uc_order_address($order, 'billing', FALSE));
  if (uc_address_field_enabled('phone') && !empty($order->billing_phone)) {
    $review[] = array('title' => t('Phone'), 'data' => check_plain($order->billing_phone));
  }
  return $review;

case 'view':
  $description = t('Use this area for special instructions or questions regarding your order.');
  if (!empty($order->order_id)) {
    $default = db_query("SELECT message FROM {uc_order_comments} WHERE order_id = :id", array(':id' => $order->order_id))->fetchField();
  }
  else {
    $default = NULL;
  }
  $contents['comments'] = array(
    '

    '

    '

  );
  return array('description' => $description, 'contents' => $contents);
case 'process':
  if (strlen($form_state['values']['panes']['comments']['comments']) > 0) {
    db_delete('uc_order_comments')
      ->condition('order_id', $order->order_id)
      ->execute();
    uc_order_comment_save($order->order_id, 0, $form_state['values']['panes']['comments']['comments'], 'order', uc_order_state_default('post_checkout'), TRUE);
  }
  return TRUE;
case 'review':
  $review = NULL;
  $result = db_query("SELECT message FROM {uc_order_comments} WHERE order_id = :id", array(':id' => $order->order_id));
  if ($comment = $result->fetchObject()) {
    $review[] = array('title' => t('Comment'), 'data' => check_plain($comment->message));
  }
  return $review;

$output = drupal_render($form['copy_address']);

if (substr($field, 0, 9) == 'delivery_' || substr($field, 0, 8) == 'billing_') {
  $title = $form[$field]['

  unset($form[$field]['

  if (substr($field, -7) == 'street1') {
    $title = uc_get_field_name('street') . ':';
  }
  elseif (substr($field, -7) == 'street2') {
    $title = ' ';
  }
  $output .= '

    $output .= $req;
  }
  $output .= $title . '

return FALSE;

if ($target['id'] == $pane_id) {
  return $prev;
}
if ($target['collapsible'] && variable_get('uc_pane' . $target['id'] . '_enabled', TRUE)) {
  $prev = $target['id'];
}

return FALSE;

if ($next) {
  if ($target['collapsible'] && variable_get('uc_pane' . $target['id'] . '_enabled', TRUE)) {
    return $target['id'];
  }
}
if ($target['id'] == $pane_id) {
  $next = TRUE;
}

return $panes;

$panes[$i]['enabled'] = variable_get('uc_pane' . $panes[$i]['id'] . 'enabled', (!isset($panes[$i]['enabled']) ? TRUE : $panes[$i]['enabled']));
$panes[$i]['weight'] = variable_get('uc_pane' . $panes[$i]['id'] . '_weight', (!isset($panes[$i]['weight']) ? 0 : $panes[$i]['weight']));
$panes[$i]['review'] = !isset($panes[$i]['review']) ? TRUE : $panes[$i]['review'];
$panes[$i]['process'] = !isset($panes[$i]['process']) ? TRUE : $panes[$i]['process'];
$panes[$i]['collapsible'] = !isset($panes[$i]['collapsible']) ? TRUE : $panes[$i]['collapsible'];

if ($pane['id'] == $pane_id) {
  return $pane[$key];
}

array('data' => t('Qty'), 'class' => array('qty')),
array('data' => t('Products'), 'class' => array('products')),
array('data' => t('Price'), 'class' => array('price')),

$total = $item->price  $item->qty;
$subtotal += $total;
$description = check_plain($item->title) . uc_product_get_description($item);
// Remove node from context to prevent the price from being altered.
$rows[] = array(
  array('data' => t('@qty×', array('@qty' => $item->qty)), 'class' => array('qty')),
  array('data' => $description, 'class' => array('products')),
  array('data' => array('

$rows[] = array(
  'data' => array(
    // One cell
    array(
      'data' => array(
        '

        '

        '

      ),
      // Cell attributes
      'colspan' => 3,
      'class' => array('subtotal'),
    ),
  ),
  // Row attributes
  'class' => array('subtotal'),
);