长轮询用PHP和AJAX ......几乎没有 [英] long polling with PHP and AJAX... almost there
本文介绍了长轮询用PHP和AJAX ......几乎没有的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正与一个学校项目。该项目的基本IDE是，我们有一些Arduino的盒子发送一些传感器数据到一个MySQL数据库，我们有一个显示该网站。传感器的数据发送可以说每6秒。
I am working with a school project. The basic ide of the project is, that we have some arduino boxes the sends some sensor data to a mysql db and we have a website that display it. Sensor data is sending lets say every 6sec.
我不有很多用PHP的经验。但我tinkerin我的方式，learing一步step..cowboy风格？ =）
I don´t have a lot of experience with PHP. But i am tinkerin my way, learing step by step..cowboy style? =)
的HTML / AJAX / CSS：
<!DOCTYPE html>
<html>
<head>
<title>Arduino event poller</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js" type="text/javascript" charset="utf-8"></script>
<style type = "text/css" media="screen">
body{ font:13px/1.5 "helvetica neue", helvetica, arial, san-serif; background:#FFF; }
#main{ width:430px; height: 300px; display:block; padding:10px 0; float: left; overflow: auto;}
.event { display:block; background: #ececec; width:380px; padding:10px; margin:10px; overflow:hidden; text-align: left; }
.event img { display:block; float:left; margin-right:10px; }
.event p { font-weight: bold; }
.event img + p { display:inline; }
.patient-name { display:inline; color: #999999; font-size: 9px; line-height:inherit; padding-left: 5px; }
.event-text{ color: #999999; font-size: 12px; padding-left: 5px; }
.event-timestamp{ color: #000; padding-left: 5px; font-size: 9px;}
</style>
<script type="text/javascript" charset="utf-8">
var timeStamp = null;
/* Simple helper to add some divs.*/
function addevents(patientroom, patientname, eventtyp, timestamp)
{
$("#main").append(
"<div class='event'>"
"<p>" + patientroom + "</p>"
"<p class='patient-name'>" + patientname + "</p>"
"<p class='event-text'>" + eventtyp + "</p>"
"<p class='event-timestamp'>" + timestamp + "</p>"
"</div>"
);
}
/*This requests the url "getevents.php" When it complete*/
function waitForEvents()
{
$.ajax({
type: "GET",
url: "getevents.php?timeStamp=" + timeStamp,
async: true, /* If set to non-async, browser shows page as "Loading.."*/
cache: false,
timeout:50000, /* Timeout in ms */
success: function(data, textStatus, jqXHR) /* called when request to getevents.php completes */
{
addevents(data.patientroom, data.patientname, data.eventtyp, data.timestamp);
setTimeout(
waitForEvents, /* Request next event */
1000 /* ..after 1 seconds */
);
},
error: function (XMLHttpRequest, textStatus, errorThrown){
alert("Error:" + textStatus + " (" + errorThrown + ")");
setTimeout(
'waitForEvents()', /* Try again after.. */
"5000"); /* milliseconds (5seconds) */
},
});
};
$(document).ready(function(){
waitForEvents(); /* Start the inital request */
});
</script>
</head>
<body>
<div id="main">
</div>
</body>
</html>
我的后端PHP：
<?php
function getEvents()
{
$con = mysql_connect("localhost","***","***");
if(!con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("arduino_db",$con);
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
if($result)
{
$patientroom = $row['rumNr'];
$patientname = $row['inneboendeNamn'];
$eventtyp = $row['handelse'];
$timestamp = $row['timestamp'];
}
if($row)
{
header('application/json');
echo json_encode($row);
exit;
}
$lastmodif = isset($_GET['timeStamp']) ? $_GET['timeStamp'] : 0;
$currentmodif = filemtime($result);
while($currentmodif <= $lastmodif)
{
unsleepp(1000);
clearstatcache();
$currentmodif = filemtime($result);
}
}
?>
我的问题：
- 如何获取我的每一行从DB和JSON格式的每一行返回到前端的方法waitForEvents。
的例子并不必须是可扩展的，安全的和完整的，它只是需要工作的 =）的
The example doesn't have to be scaleable, secure or complete, it just needs to work =)
更新：根据约翰提示新的code。所有我得到是一个空白页，并没有错误。
UPDATE: new code based on Johns tips. All I gets is a blank page, and no errors.
推荐答案
这突然出现给我看的第一件事是有点您的MySQL电话响起。
The first thing that popped out to me is that your MySQL call is sort of blown.
在运行这一行：
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
您会得到一个MySQL的资源。你需要利用这让你的行：
You're going to get a MySQL resource. You need to utilize that to get your row:
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
if ($result)
{
$row = mysql_fetch_assoc($result);
if ($row)
{
// Your result is here, as a big associative array. Each column in your
// table is now keyed to this array. Exact fields will depend on your DB.
//
// Just access it like something like this:
$id = $row['id'];
$time = $row['time_stamp'];
}
}
呼应回了为JSON：
to echo it back out as JSON:
... // snip
if ($row)
{
header('application/json');
echo json_encode($row);
exit;
}
}
// handle your errors!
补充：OP中发现的问题更多的错误的：
added: Additional error found in OP question:
// The following line isn't valid. This isn't what you'll get back from $.ajax.
// success: function(patientroom, patientname, eventtyp, timestamp)
// Corrected code:
success: function(data, textStatus, jqXHR)
/* called when request to getevents.php completes */
{
addevents(data.patientroom, data.patientname, data.eventtyp, data.timestamp);
setTimeout(
waitForEvents, /* Request next event */
1000 /* ..after 1 seconds */
);
},
进一步更新。你混合＆放大器;从上面匹配code。
Further updates. You mixed & matched the code from above.
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
if($result)
{
// this has to go inside of this check. This is where you *ASSIGN* $row.
$row = mysql_fetch_assoc($result);
// You need to rekey $row before you output:
$retVal = array('patientroom'=>$row['rumNr'],
'patientname'=>$row['inneboendeNamn'],
'eventtyp'=>$row['handelse'],
'timestamp'=>$row['timestamp']);
// I'm not sure what you're doing with the incoming timestamp. Should we just
// return it back out?
$retVal['ajax_timestamp'] = $_GET['timeStamp'];
header('application/json');
echo json_encode($retVal);
exit; // this exits. Comment this out if you want, but don't try to write anything else out to the buffer.
}
// Not sure what you're trying to do here. I'll comment out for now.
/*
$lastmodif = isset($_GET['timeStamp']) ? $_GET['timeStamp'] : 0;
$currentmodif = filemtime($result);
while($currentmodif <= $lastmodif)
{
unsleepp(1000);
clearstatcache();
$currentmodif = filemtime($result);
}
*/
}
这篇关于长轮询用PHP和AJAX ......几乎没有的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
查看全文
