我正在与一个学校项目合作。该项目的基本思想是，我们有一些arduino盒子将一些传感器数据发送到mysql数据库，我们有一个显示它的网站。传感器数据发送可以说每6秒。
我没有很多PHP经验。但我正在修补我的方式，一步一步地学习......牛仔风格？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：
该示例不必是可扩展的，安全的或完整的，只需要工作 =）
更新：基于Johns提示的新代码。我得到的只是一个空白页，没有错误。
答案 0 :(得分：2)
对我来说，第一件事就是你的MySQL调用很糟糕。
当您运行此行时：
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
您将获得MySQL资源。你需要利用它来获得你的行：
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
if ($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 = $row['time_stamp'];
}
}
以JSON回显它：
... // snip
if ($row)
{
header('application/json');
echo json_encode($row);
exit;
}
}
// handle your errors!
补充：OP问题中发现了其他错误：
// 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。你混合了＆amp;匹配上面的代码。
$result = mysql_query("SELECT * FROM events ORDER BY eventID DESC LIMIT 1");
if($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);
}
*/
}
答案 1 :(得分：0)
我知道你不应该用php进行长轮询。如果你不是一个专业的php-hacker，还有很多其他原因，那就太乱了。
我的项目需要的是显示新数据而不刷新漏洞网站。我是这样做的：
<script type="text/javascript">
var timeoutId;
var intervalId;
function doIt(){
$("#main").load("refresh.php");
}
$(document).ready(function(){
timeoutId = setTimeout(function(){
doIt();
intervalId = setInterval(function(){
doIt();
}, 5000); //Request the doIt() method every 5ms.
}, 3000); //Delay calculated on the server to trigger the function at the appropriate time
});
</script>