使用新的mysqli查询获取多行？

Question

I'm using php to connect to mysql database and am using the following function to retrieve multiple rows from database and then add them to an array and send them back. I'm getting internal server error or 500x error messages. I'm not sure what is wrong with this code. I've tried to figure it out but can't get it.

public function getUnreadMessages($uname){
          $stmt = $this->conn->prepare("SELECT msgid, title, fromuname FROM messages WHERE touname = ? and status = ?");
          $status = 'unread';
        $stmt->bind_param("ss", $uname, $status);
        if ($stmt->execute()) {
                $stmt->bind_result($col1, $col2, $col3);
                $stmt->store_result();
                $resp = array();
            while($stmt->fetch()){
                        $row = array();
                        array_push($row, $col1, $col2, $col3);
                        array_push($resp, $row);            
            }
            $msg = array('msgid' => $msgid,'title' => $title,'fromuname' => $fromuname);
            $stmt->close();
            return $msg;

        } else {
                        $stmt->close();
                     return NULL;
        }
    }

how should I go about doing this? The function that handles the returned results are as follows

$app->get('/inbox', 'authenticate', function() use ($app){
        ob_start("ob_gzhandler");
        global $global_user_name;
        $db = new DbHandler();
        $resp = $db->getUnreadMessages($global_user_name);
        $msgs = array();
        $msgs['status'] = 'success';
        $msgs['version'] = 0.1;
        array_push($msgs, $resp);

        $app->response()->header('Content-Type', 'application/json');
        echo json_encode($msgs);
        exit;

});

Answer 1

The PDO method automating this is $stmt->fetchAll() :D

public function getUnreadMessages($uname)
{
    $stmt = $this->conn->prepare("SELECT msgid,title,fromuname FROM messages WHERE touname = ? and status = ?");
    $stmt->execute([$uname, 'unread']))
    return $stmt->fetchAll(PDO::FETCH_ASSOC);
}

Return false if nothing has been found or something like :

$msg = [
    [
        'msgid' => 2746,
        'title' => 'Random title',
        'fromuname' => 'SomeGuy'
    ],
    [
        'msgid' => 754,
        'title' => 'Some title',
        'fromuname' => 'Random Name'
    ],
    [
        'msgid' => 27686,
        'title' => 'Unreadable title',
        'fromuname' => 'Training dummies'
    ],
];

Answer 2

I've solved my question. It was that I was creating an array within a loop. This seems to be disallowed. Here's the code that did work in the end

public function getUnreadMessages($uname){

            $stmt = $this->conn->prepare("SELECT msgid, title, fromuname FROM messages WHERE touname = ? and status = ?");
                $status = 'unread';
                $stmt->bind_param("ss", $uname, $status);
            $result = $stmt->execute();
            $stmt->bind_result($col1, $col2, $col3);
            $stmt->store_result();
            $outer = array();
            $inner = array();
            while($stmt->fetch()){
                    array_push($inner, $col1, $col2, $col3);
            }
            array_push($outer, $inner);
            return $outer;
            $stmt->close();
    }