使用jQuery和PHP实现长轮询

您不想创建无限循环,但可以设置超时.基本上循环为X秒等待某种数据,如果没有发生,则向客户端发送响应,告诉它需要发起新请求,该请求具有相同的超时时间.

$source; // some data source - db,etc
$data = null; // our return data
$timeout = 30; // timeout in seconds
$Now = time(); // start time

// loop for $timeout seconds from $Now until we get $data
while((time() - $Now) < $timeout) {
    // fetch $data
    $data = $source->getData();

    // if we got $data,break the loop
    if (!empty($data)) break;

    // wait 1 sec to check for new $data
    usleep(10000);
}

// if there is no $data,tell the client to re-request (arbitrary status messagE)
if (empty($data)) $data = array('status'=>'no-data');

// send $data response to client
echo json_encode($data);