Newbie: Fatal error: Using $this when not in object context - URI Helper.

[eluser]MEM[/eluser]
When the CI User Guide states:

Note: This class is initialized automatically by the system so there is no need to do it manually.

What does this mean? It means that we don't need to create an instance of a class?

I was trying to use the following on my View:

Code:

if($this->uri->segment(3)==$arrMenu[i][$strChildKey]['id_cat'])
{

I'm getting an error:

Using $this when not in object context in /home/akasite/private/application/views/v_categoria.php on line 111

What's the issue?

Márcio