You can render a block in PHP as follow.
... $block = (object) module_invoke('<module>', 'block', 'view', "<block id>"); print theme('block', $block); ...
If your block is a create by Views, then the <module> is views. For other normal blocks, just simply use block. And you can find out the <block id> @ Adminster -> Site building -> Blocks as depicted below.
Move your mouse to the configure link and you can find the block id. In the above picture, the block id is latest_search-block_1.