simplenews subscription form on front page with frontpage module
Try this:

&lt;?php $block = module_invoke('simplenews','block_view',5); print render($block); ?&gt;


The number 5 shouldn't be sent as a string.

And if you are putting this in a textarea on Drupal's backend, you need the PHP input filter, which is generally a bad idea.  Better to go through the theming system, add a region, and put the block there.

http://drupal.org/node/1088718