WordPress Version check with PHP

Try checking the attribute contents before setting the value:

$generator=""; // clear previous value
for ($i = 0; $i < $metas->length; $i++)
    {
        $meta = $metas->item($i);
        if($meta->getAttribute('name') == 'description')
            $description = $meta->getAttribute('content');

        if($meta->getAttribute('name') == 'generator') {
            $thisgenerator = $meta->getAttribute('content');
            if ( ($generator == '') && (stristr($thisgenerator,'wordpress')) ) {
                $generator = $thisgenerator;
            }
        }
    }