PHPStorm: method xpath not found in class. How to "teach" the IDE to find methods?

Question

phpstorm

I'm tormented by words to explain, I'd rather show a gif:

A simple wrapper class. When choosing a method for $this-svg , the possible methods in the list are substituted, and then the method is immediately highlighted as not found.
Interestingly, this behavior does not always take place ! For example, for a wrapper over PDO, sometimes everything is fine, sometimes method prepare() not found in class .
Tried to google, but could not formulate a request.
wtf? CHADNT?

Answer 1

And if you specify php-doc?

class ParseSVG {
    /**
     * @var SimpleXMLElement
     */
    private $svg;
}