DOMDocument::loadHTML() Source must not be empty error when inputting result from curl_multi_getcontent()

Question

Using curl_multi_init and querypath in a php environment, I am querying multiple websites and then reading the query results which should all be all HTML format. I process the results by using curl_multi_getcontent(). When using the results as input for Querypath to manually parse the results, I get this error:

DOMDocument::loadHTML(): Argument #1 ($source) must not be empty ...

This is my code:

[... running in a loop for every request]    
$results = curl_multi_getcontent ($curl_arr[$i]);
$htmlString = (string) $results; //casting the result to string
        
//echo $htmlString;         //gives me the correct html result!
//echo strlen($htmlString); //proves that string is not empty!?
        
$qp = QueryPath::withHTML($htmlString); //this line is causing the error

I don't know what I might be missing. Any hints?

Answer 1

It seems that I ran into an encoding problem. It worked once I changed $htmlString = (string) $results; into $htmlString = utf8_decode($results);