How to execute a query on tin-can statements?

I am using Learning Locker (Learning Record Store). I succeed inserting statements to it via the REST API. But I did not succeed fetching statements from it. How do I preform a query on statements? REST API?

I used tinCanPhp library. This is how you establish a connection with the Learning Locker database and query it in PHP. For example:

    $lrs = new TinCan\RemoteLRS(
            'endpoint/public/data/xAPI/',
            '1.0.1',
            'username',
            'key'
    );

    $actor = new TinCan\Agent(
            [ 'mbox' => 'mailto:dikla@gmail.com' ]
    );
    $verb = new TinCan\Verb(
            [ 'id' => 'http://adlnet.gov/expapi/verbs/progressed' ]
    );
    $activity = new TinCan\Activity(
            [ 'id' => 'http://game.t-shirt' ]
    );
    $statement = new TinCan\Statement(
            [
            'actor' => $actor,
            'verb'  => $verb,
            'object' => $activity,
            ]
    );

    //get All Actor activity by his unique id
    function getAllActorActivity($actorUri){
        global $lrs;
        $actor = new TinCan\Agent(
                [ 'mbox' => $actorUri ]//actorUri should look like this 'mailto:dikla@gmail.com'
        );
        $answer=$lrs->queryStatements(['agent' => $actor]);
        return $answer;
    }