关于用POST方法发送JSON数据的有关问题

$opts = array(
    'http' => array(
        'method' => 'POST',
        'header' => 'content-type:application/x-www-form-urlencoded',
        'user_agent' => $_SERVER['HTTP_USER_AGENT'],
        'content' => http_build_query($data)
    )    
);
 
$context = stream_context_create($opts);
$result = file_get_contents($url, false, $context);