Call to a member function on a non-object [duplicate]

Answer 1

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 featureDocs 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.