我正在尝试评估json响应，这是代码 调用json响应：
<style type="text/css" media="screen">
.chat_time {
font-style: italic;
font-size: 9px;
}
</style>
<script language="JavaScript" type="text/javascript">
var sendReqCon = getXmlHttpRequestObject();
var receiveReqCon = getXmlHttpRequestObject();
var lastMessageCon = 0;
var mTimerCon;
//Function for initializating the page.
function startCon() {
//Set the focus to the Message Box.
document.getElementById('txt_context').focus();
//Start Recieving Messages.
getConText();
}
//Gets the browser specific XmlHttpRequest Object
function getXmlHttpRequestObject() {
if (window.XMLHttpRequest) {
return new XMLHttpRequest();
} else if(window.ActiveXObject) {
return new ActiveXObject("Microsoft.XMLHTTP");
} else {
document.getElementById('p_status').innerHTML = 'Status: Cound not create XmlHttpRequest Object. Consider upgrading your browser.';
}
}
//Gets the current messages from the server
function getConText() {
if (receiveReqCon.readyState == 4 || receiveReqCon.readyState == 0) {
receiveReqCon.open("GET", 'getCon.php?con=<?php echo $topic_id ?>&last=' + lastMessageCon, true);
receiveReqCon.onreadystatechange = handleReceiveCon;
receiveReqCon.send(null);
}
}
//Add a message to the chat server.
function sendConText() {
if(document.getElementById('txt_context').value == '') {
alert("You have not entered a context");
return;
}
if (sendReqCon.readyState == 4 || sendReqCon.readyState == 0) {
sendReqCon.open("POST", 'getCon.php?con=<?php echo $topic_id ?>&last=' + lastMessageCon, true);
sendReqCon.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
sendReqCon.onreadystatechange = handleSendCon;
var param = 'context=' + document.getElementById('txt_context').value;
param += '&namecon=<?php echo $user_name?>';
param += '&con=1';
param += '&uidcon=<?php echo $logged_user?>';
sendReqCon.send(param);
document.getElementById('txt_context').value = '';
}
}
//When our message has been sent, update our page.
function handleSendCon() {
//Clear out the existing timer so we don't have
//multiple timer instances running.
clearInterval(mTimerCon);
getConText();
}
function handleReceiveCon() {
if (receiveReqCon.readyState == 4) {
//Get a reference to our chat container div for easy access
var con_div = document.getElementById('div_con');
// con_div.innerHTML+='check this div';
//Get the AJAX response and run the JavaScript evaluation function
//on it to turn it into a useable object. Notice since we are passing
//in the JSON value as a string we need to wrap it in parentheses
con_div.innerHTML= 'receiveReqCon.responseXML';
var response = eval("(" + receiveReqCon.responseXML + ")");
echo ('response');
for(i=0;i < response.cont.context.length; i++) {
con_div.innerHTML += '<b>'+response.cont.context[i].user+'</b>';
con_div.innerHTML += ' <font class="chat_time" style="color:black;">' + response.cont.context[i].time + '</font><br />';
// con_div.innerHTML += '<p style="color:black;">'+response.messages.context[i].text + '</p>';
con_div.innerHTML += 'hello';
con_div.scrollTop = chat_div.scrollHeight;
lastMessageCon = response.cont.context[i].id;
}
mTimerCon = setTimeout('getConText();',2000); //Refresh our chat in 2 seconds
}
}
//This functions handles when the user presses enter. Instead of submitting the form, we
//send a new message to the server and return false.
//
function blockSubmit1() {
sendConText();
return false;
}
//This cleans out the database so we can start a new chat session.
function resetCon() {
if (sendReqCon.readyState == 4 || sendReqCon.readyState == 0) {
sendReqCon.open("POST", 'getCon.php?chat=1&last=' + lastMessageCon, true);
sendReqCon.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
sendReqCon.onreadystatechange = handleResetChat;
var param = 'action=reset';
sendReqCon.send(param);
document.getElementById('txt_context').value = '';
}
}
//This function handles the response after the page has been refreshed.
function handleResetCon() {
document.getElementById('div_con').innerHTML = '';
getConText();
}
</script>
创建json响应：
<?php
//Send some headers to keep the user's browser from caching the response.
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT" );
header("Last-Modified: " . gmdate( "D, d M Y H:i:s" ) . "GMT" );
header("Cache-Control: no-cache, must-revalidate" );
header("Pragma: no-cache" );
header("Content-Type: text/plain; charset=utf-8");
require('database.php');
//Check to see if a message was sent.
if(isset($_POST['context']) && $_POST['context'] != '') {
$c_id=db_input($_GET['con']);
$u_id=db_input($_POST['uidcon']);
$u_name=db_input($_POST['namecon']);
$msg=db_input($_POST['context']);
$sql = "INSERT INTO context(topic_id,user_id,user_name,context,context_time, status) VALUES ('$c_id','$u_id','$u_name','$msg',now(),'1')";
db_query($sql);
}
//Check to see if a reset request was sent.
if(isset($_POST['action']) && $_POST['action'] == 'reset') {
$sql = "DELETE FROM message WHERE chat_id = " . db_input($_GET['chat']);
db_query($sql);
}
//Create the JSON response.
$json = '{"cont": {';
//Check to ensure the user is in a chat room.
if(!isset($_GET['con'])) {
$json .= '"context":[ {';
$json .= '"id": "0",
"user": "Admin",
"text": "You are not currently in a chat session. <a href="">Enter a chat session here</a>",
"time": "' . date('h:i') . '"
}]';
}
else {
$last = (isset($_GET['last']) && $_GET['last'] != '') ? $_GET['last'] : 0;
// $sql = "SELECT message_id, user_name, message, date_format(post_time, '%h:%i %p') as post_time" .
// " FROM message WHERE chat_id = " . db_input($_GET['chat']) . " AND message_id > " . $last;
// $sql = "SELECT context_id, user_name, context, date_format(context_time, '%h:%i %p') as context_time" .
// " FROM context WHERE topic_id = " . db_input($_GET['con']) . " AND context_id > " . $last;
$sql = "SELECT context_id, user_name, context, date_format(context_time, '%h:%i %p') as context_time" .
" FROM context";
$context_query = db_query($sql);
//Loop through each message and create an XML message node for each.
if(db_num_rows($context_query) > 0) {
$json .= '"context":[ ';
while($context_array = db_fetch_array($context_query)) {
$json .= '{';
$json .= '"id": "' . $context_array['context_id'] . '",
"user": "' . htmlspecialchars($context_array['user_name']) . '",
"text": "' . htmlspecialchars($context_array['context']) . '",
"time": "' . $context_array['context_time'] . '"
},';
}
$json .= ']';
} else {
//Send an empty message to avoid a Javascript error when we check for message lenght in the loop.
$json .= '"context":[]';
}
}
//Close our response
$json .= '}}';
echo $json;
?>
我无法评估json响应，我认为符合“var response = eval（”（“+ receiveReqCon.responseXML +”）“）;”
请建议我的解决方案。 提前致谢
答案 0 :(得分：0)
首先看你应该替换
header("Content-Type: text/plain; charset=utf-8");
用
header("Content-Type: application/json; charset=utf-8");
此外，在JS中解码JSON的最简单方法是使用JSON.parse(json);函数。看一下这个例子：
var json_string = '{"result":true,"string":"test"}',
json_obj = JSON.parse(json_string);
// Write in console / alert dialog
console.log(json_string.result); alert(json_string.result);
在服务器端，您不应该自己创建JSON对象。使用内置函数json_encode($array)的PHP。使用您自己的代码查看我的示例：
//Create the JSON response.
$json_obj = array();
/*
* $json = '{"cont": {';
*/
//Check to ensure the user is in a chat room.
if(!isset($_GET['con'])) {
$json_obj['cont']['context'][] = array(
'id' => 0,
'user' => 'Admin',
'text'=> "You are not currently in a chat session. <a href=\"\">Enter a chat session here</a>",
'time' => date('h:i')
)
/*
$json .= '"context":[ {';
$json .= '"id": "0",
"user": "Admin",
"text": "You are not currently in a chat session. <a href="">Enter a chat session here</a>",
"time": "' . date('h:i') . '"
}]';
*/
} else { /*you do the rest of the job here*/ }
// at the end of php script you write:
echo json_encode($json_obj, JSON_PRETTY_PRINT);
exit();
?>