How to display different Static Blocks based on Category in Magento

The code below can be used in the template/page .phtml files and has been used in the 2column-left.phtml file:

<?php $category = Mage::getModel('catalog/layer')->getCurrentCategory();?>
<?php if($category->getId()==24): ?>
<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('block-for-cat24')->toHtml() ?>
<?php elseif($category->getId()==23): ?>
<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('block-for-cat23')->toHtml() ?>
<?php else: ?>
<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('block-for-everything-else')->toHtml() ?>
<?php endif; ?>