How to use the $delta argument?

Question

How do I use the $delta argument in hook_block?

I have tried to used one, but there wasn't any effect.

What is the correct way to do this?

Answer 1

/**
 * Implementation of hook_block().
 */
function YOURMODULE_block($op = 'list', $delta = 0, $edit = array()) {
  switch ($op) {
    case 'list':
      $blocks[0]['info'] = t('Block #1 name');
      $blocks[1]['info'] = t('Block #2 name');
      return $blocks;
    case 'view':
      $block = array();
      switch ($delta) {
        case 0:
          $block['content'] = t('Hello for block #1');
          break;
        case 1:
          $block['content'] = t('Hello for block #2');
          break;
      }
      return $block;
  }
}

Answer 2

As noted elsewhere, $delta allows one module to return many blocks. It may also be easier to understand if you keep in mind that the $delta need not be numeric. It's simply an identifier.

You use the $delta first when responding to the 'list' $op. Each key in the $block array you return will be a $delta that can be used to configure or render that specific block.

switch ($op) {
    case 'list':
      $block['sidebar-links']['info'] = t('Sidebar Links');
      $block['footer-links']['info'] = t('Footer Links');
      return $block;

What this is telling the Drupal system is that the module in question has two blocks, one of which is identified by "sidebar-links", the other by "footer-links".

This will place two blocks on the admin/build/block config page. Should you enable both blocks, they will then be rendered by calls to the 'view' $op with the identifying key as the $delta:

    case 'view':
      switch ($delta) {
        case 'sidebar-links': 
          $block['subject'] = t('Sidebar Links');
          $block['content'] = "super weak";
          break;
        case 'footer-links':
          $block['subject'] = t('Footer Links');
          $block['content'] = "super weak";
          break;
      }
      return $block;
  }

As an added bonus, using semantic keys for your blocks will result in easier to read CSS id's. :)

Answer 3

An implementation of HOOK_block() can contain multiple blocks. The $delta argument specifies to the function which block to output. Example:

/**
 * Implementation of hook_block().
*/
function fightfi_block($op = 'list', $delta = 0) {
  $block = array();
  switch ($op) {
    case 'list':
      $block[0]['info'] = t('Sidebar Links');
      $block[1]['info'] = t('Footer Links');
      return $block;
    case 'view':
      switch ($delta) {
        case 0: 
          $block['subject'] = t('Sidebar Links');
          $block['content'] = "super weak";
          break;
        case 1:
          $block['subject'] = t('Footer Links');
          $block['content'] = "super weak";
          break;
      }
      return $block;
  }
} // end function fightfi_block

Answer 4

It is better to see the example module for all kind of drupal examples.. http://drupal.org/project/examples You will find block example over here....