Quick fix to $this can not be used in static methods?

Question

is there any quick fix to this? I'm not a PHP developer so it's a bit hard to fix it myself neither can I afford a developer... but I'd appreciate any help Thanks.

$this can not be used in static methods.

                 { 
                    $node = $dom->createElement($key);
                    if ($value != NULL) 
                    {
                        foreach ($value as $key => $value) 
                        {
                            $sub = $this->createNode($key, $value);
                            if ($sub != NULL)
                            {
                                $node->appendChild($sub);
                            }    
                        }
                    }
                }

imgur.com/SYAHz.png

Answer 1

try

                 { 
                    $node = $dom->createElement($key);
                    if ($value != NULL) 
                    {
                        foreach ($value as $key => $value) 
                        {
                            $sub = $dom->createNode($key, $value);
                            if ($sub != NULL)
                            {
                                $node->appendChild($sub);
                            }    
                        }
                    }
                }