Warning: session_start(): Cannot start session when headers already sent in D:\wampserver\www\new b2\index.php on line 351
时间: 2023-11-28 12:04:55 浏览: 46
这个错误提示是因为在您的PHP代码中,在输出HTTP头信息之前使用了session_start()函数。在调用session_start()函数之前,确保没有输出任何内容(包括空格和换行符)到浏览器。您可以尝试将session_start()函数调用放在所有的header()函数之前,或者在代码中使用ob_start()函数来缓存输出,以确保session_start()函数在输出HTTP头信息之前被调用。
相关问题
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
This error occurs when you are trying to send HTTP headers to the client (i.e. the user's browser) after they have already been sent. Once the headers have been sent, they cannot be modified or sent again.
This error typically occurs when there is a logic error in your code, such as sending headers in a loop or sending headers after the response has already been sent.
To fix this error, you will need to carefully review your code and ensure that you are only sending headers once, and that they are being sent before any response data is sent. You may also need to refactor your code to ensure that headers are only being sent in the appropriate places.
Here are a few tips to help you avoid this error:
1. Make sure that you are not sending headers in a loop or conditional statement that may be executed multiple times.
2. If you are using middleware or other third-party libraries, make sure that they are not sending headers after the response has already been sent.
3. Use a tool like Postman or a browser extension like Live HTTP Headers to inspect the headers that are being sent and received, and look for any anomalies that may be causing the error.
4. If you are still having trouble, try using a debugger to step through your code and identify where the headers are being sent and why they may be causing an error.
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the
这个错误是由于在服务端重复发送响应导致的。通常情况下,如果在代码中多次使用res.send()或者同时使用res.send()和res.writeHead(),就会出现这个错误。解决这个问题的方法是,确保只有一次发送响应的操作,并且在发送响应后立即返回,避免继续执行后续的发送响应操作。
例如,在你提供的例子中,通过在出现问题的地方添加return关键字来立即返回,可以解决这个问题:
```
db.query(sqlStr, userinfo.username, (err, result) => {
if (err) {
return res.send({ status: 1, message: err.message });
}
if (result.length > 0) {
return res.send({ status: 1, msg: '用户名被占用' });
}
// 用户名可以使用
res.send("ok");
})
```
另外,如果在代码中使用了res.writeHead()函数,然后再使用res.send()方法,也会导致这个错误。在这种情况下,你可以使用res.end()方法来结束响应,而不再使用res.send()方法。
```
const body = 'hello https://zhengkai.blog.csdn.net/';
response.writeHead(200, {
'Content-Length': Buffer.byteLength(body),
'Content-Type': 'text/json;charset=utf-8',
}).end(body);
```
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