php - Call to a member function on a non-object

So I'm refactoring my code to implement more OOP. I set up a class to hold page attributes.

class PageAtrributes 
{
  private $db_connection;
  private $page_title;


    public function __construct($db_connection) 
    {
        $this->db_connection = $db_connection;
        $this->page_title = '';
    }

    public function get_page_title()
    {
        return $this->page_title;

    }

    public function set_page_title($page_title)
    {
        $this->page_title = $page_title;
    }
}

Later on I call the set_page_title() function like so

function page_properties($objPortal) {    
    $objPage->set_page_title($myrow['title']);
}

When I do I receive the error message:

Call to a member function set_page_title() on a non-object

So what am I missing?

Answer

It means that $objPage is not an instance of an object. Can we see the code you used to initialize the variable?

As you expect a specific object type, you can also make use of PHPs type-hinting feature^Docs to get the error when your logic is violated:

function page_properties(PageAtrributes $objPortal) {    
    ...

    $objPage->set_page_title($myrow['title']);
}

This function will only accept PageAtrributes for the first parameter.