Multiple Queries in MQL on Freebase

Question

I am trying to get a list of results from Freebase. I have an array of MIDs. Can someone explain how I would structure the query and pass it to the API in PHP?

I'm new to MQL - I can't even seem to get the example to work:

$simplequery = array('id'=>'/topic/en/philip_k_dick', '/film/writer/film'=>array());
$jsonquerystr = json_encode($simplequery);
// The Freebase API requires a query envelope (which allows you to run multiple queries simultaneously) so we need to wrap our original, simplequery structure in two more arrays before we can pass it to the API:
$queryarray = array('q1'=>array('query'=>$simplequery));
$jsonquerystr = json_encode($queryarray);
// To send the JSON formatted MQL query to the Freebase API use cURL:
#run the query
$apiendpoint = "http://api.freebase.com/api/service/mqlread?queries";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "$apiendpoint=$jsonquerystr");
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$jsonresultstr = curl_exec($ch);
curl_close($ch);
// Decoding the JSON structure back into arrays is performed using json_decode as in:
$resultarray = json_decode($jsonresultstr, true); #true:give us the json struct as an array
// Iterating over the pieces of the resultarray containing films gives us the films Philip K. Dick wrote:
$filmarray = $resultarray["q1"]["result"]["/film/writer/film"];

foreach($filmarray as $film){
    print "$film<br>";
}

Answer 1

You're doing everything right. If you weren't, you'd be getting back error messages in your JSON result.

I think what's happened is that the data on Philip K. Dick has been updated to identify him not as the "writer" of films, but as a "film_story_contributor". (He didn't, after all, actually write any of the screenplays.)

Change your simplequery from:

$simplequery = array('id'=>'/topic/en/philip_k_dick', '/film/writer/film'=>array());

To:

$simplequery = array('id'=>'/topic/en/philip_k_dick', '/film/film_story_contributor/film_story_credits'=>array());

You actually can use the Freebase website to drill down into topics to dig up this information, but it's not that easy to find. On the basic Philip K. Dick page (http://www.freebase.com/view/en/philip_k_dick), click the "Edit and Show details" button at the bottom.

The "edit" page (http://www.freebase.com/edit/topic/en/philip_k_dick) shows the Types associated with this topic. The list includes "Film story contributor" but not "writer". Within the Film story contributor block on this page, there's a "detail view" link (http://www.freebase.com/view/en/philip_k_dick/-/film/film_story_contributor/film_story_credits). This is, essentially, what you're trying to replicate with your PHP code.

A similar drill-down on an actual film writer (e.g., Steve Martin), gets you to a property called /film/writer/film (http://www.freebase.com/view/en/steve_martin/-/film/writer/film).

Multiple Queries

You don't say exactly what you're trying to do with an array of MIDs, but firing multiple queries is as simple as adding a q2, q3, etc., all inside the $queryarray. The answers will come back inside the same structure - you can pull them out just like you pull out the q1 data. If you print out your jsonquerystr and jsonresultstr you'll see what's going on.

Answer 2

Modified a bit to include answer into question, as this helped me I've upvoted each, just thought I would provide a more "compleat" answer, as it were:

$simplequery = array('id'=>'/topic/en/philip_k_dick', '/film/film_story_contributor/film_story_credits'=>array());
$jsonquerystr = json_encode($simplequery);
// The Freebase API requires a query envelope (which allows you to run multiple queries simultaneously) so we need to wrap our original, simplequery structure in two more arrays before we can pass it to the API:
$queryarray = array('q1'=>array('query'=>$simplequery));
$jsonquerystr = json_encode($queryarray);
// To send the JSON formatted MQL query to the Freebase API use cURL:
#run the query
$apiendpoint = "http://api.freebase.com/api/service/mqlread?queries";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "$apiendpoint=$jsonquerystr");
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$jsonresultstr = curl_exec($ch);
curl_close($ch);
// Decoding the JSON structure back into arrays is performed using json_decode as in:
$resultarray = json_decode($jsonresultstr, true); #true:give us the json struct as an associative array
// Iterating over the pieces of the resultarray containing films gives us the films Philip K. Dick wrote:

if($resultarray['code'] == '/api/status/ok'){
    $films = $resultarray['q1']['result']['/film/film_story_contributor/film_story_credits'];
    foreach ($films as $film){
        print "$film</br>";
    }
}