Block not rendering

Question

In my backend controller I use the following code to render a custom block.

 $this->_title($this->__('Inventar'));
 $this->loadLayout();
 $this->_setActiveMenu('psp_inventorymanager');
 $this->_addContent($this->getLayout()->createBlock('psp_inventorymanager/adminhtml_importstatus'));
 $this->_initLayoutMessages('customer/session');
 $this->renderLayout();

But the _addContent line does not work. It works on a local magento install but not on the main site. This is the content of the block's _toHtml():

 public function _toHtml()
 {
 $html = parent::_toHtml();
 $session = Mage::getSingleton('core/session');
 echo '<style>
 .list-with-heading h3{
 font-weight: normal;
 }
 .list-success {
 background: green;
 }
 .list-fail {
 background: red;
 }
 .list-oldqty {
 background: yellow;
 }
 .list-with-heading {
 background: #00BFFF;
 border: 1px solid #000;
 padding: 10px;
 }
 .auto {
 max-height: 150px;
 overflow: auto;
 border: 1px solid #000;
 padding: 10px;
 }
 </style>';
 echo '<div class="list-with-heading"><h3>Successful imports: </h3><ul class="list-success auto">';
 foreach ($session->getInventoryImportSuccess() as $key => $value) {
 echo '<li>'. $key .'</li>';
 }
 echo '</ul></div>';
 echo '<div class="list-with-heading"><h3>Failed imports [SKU not found]: </h3><ul class="list-fail auto">';
 foreach ($session->getInventoryImportFail() as $key => $value) {
 echo '<li>'. $key .'</li>';
 }
 echo '</ul></div>';
 echo '<div class="list-with-heading"><h3>Failed imports [QTY not changed]: </h3><ul class="list-oldqty auto">';
 foreach ($session->getInventoryImportOldQty() as $key => $value) {
 echo '<li>'. $key .'</li>';
 }
 echo '</ul></div>';
 $html .= "teeeeeeeeeeeeest";
 return $html;
 }

Edit: I have looked at the system.log and createBlock fails and returns false instead of the block.

Answer 1

I feel silly now. I traced createBlock and saw that I had a typo in my block's naming. I had to change

->createBlock('psp_inventorymanager/adminhtml_importstatus')

to this

->createBlock('psp_inventorymanager/adminhtml_importStatus')