MultiBlock - Multiple instances of a block

PROBLEM

Drupal's block module is limited by the fact that a block can only have one instance. Each block has a 1:1 relationship with its region, weight, visibility (and other) settings. This means that it is impossible to have blocks in multiple regions or to have blocks that have different settings on different pages.

SOLUTION

The Multiblock module will keep track of multiple instances of blocks and dispatch to their appropriate block hooks.

Using this strategy, you would not enable any blocks that are implemented by other modules. Instead, you will go to admin/build/block/instances and create an "instance" of a block. The Multiblock module will then implement this block in its own block hook which will forward any hook_block calls to the original module's hook.

Using this method we can maintain multiple instances of blocks with different settings but the same implementation. This should not affect block-level caching.

One catch here is that the configure and save $op's for hook_block are usually implemented to save only one set of data. This means that for blocks that are unaware of Multiblock you will only be able to save CUSTOM data (this doesn't include visibility, weight, region, etc.) for one set of data.

HOW TO USE IT

1. Go to
   • admin/build/block/instances (Drupal 6)
   • admin/structure/block/instances (Drupal 7)
2. Select the type of block you want to create an instance of and type a unique title for that instance
3. Click "Add Instance"
4. Go to
   • admin/build/block (Drupal 6)
   • admin/structure/block (Drupal 7)
5. Enable the block instance you have just created.

DEVELOPING MULTIBLOCK-ENABLED BLOCKS

Multiblock should successfully clone any regular block created with hook_block. However, if you clone a regular block that implements a save or configure $op of hook_block, the custom block settings of one block instance will overwrite the settings of another.

To get around this, you can make a block "multiblock enabled". To do this, you have to first add an $op to your hook_block called 'mb_enabled'. It should always return the string 'mb_enabled'.

Once you do this, the instances you create will get the block instance ID passed in the $edit variable for the view, configure, and save $ops. This will let you save and load different data to different instances based on this instance ID. It is passed in with the multiblock_delta key with the following format:

  $edit['multiblock_delta'] = array(
    '#type' => 'value',
    '#value' => $block_id,
    );

Preventing Multiblock Instances

Modules can block themselves by adding another case to their hook_block (as does Multiblock itself). If a module wants to block MB, it can implement op='mb_blocked' and return the module name as a string. For example:

function multiblock_block($op = 'list', $delta = 0, $edit = array()) {
  switch ($op) {
    case 'mb_blocked':
      return 'multiblock';
...

With this in place, admins will not be able to add instances of blocks from the blocked module. This could be useful in modules that already provide multiple instances of their blocks.