php 如何解决：session_start()：无法发送会话缓存限制器 - 已发送标头
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How to solve: session_start(): Cannot send session cache limiter - headers already sent
提问by CatUser
How to solve this error (session_start(): Cannot send session cache limiter - headers already sent (output started at /opt/lampp/htdocs/hrms/header.php:140))? This is login page.
如何解决此错误（session_start()：无法发送会话缓存限制器 - 已发送标头（输出开始于 /opt/lampp/htdocs/hrms/header.php:140））？这是登录页面。
Logs:
日志：
PHP Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /opt/lampp/htdocs/hrms/header.php:140) in /opt/lampp/htdocs/hrms/index.php on line 74
PHP Warning: Cannot modify header information - headers already sent by (output started at /opt/lampp/htdocs/hrms/header.php:140) in /opt/lampp/htdocs/hrms/index.php on line 82
line 74:
第 74 行：
session_start();
line 82:
第 82 行：
header('location:home.php');
Page:
页：
<?php include('dbcon.php');include('header.php');?>
<body>
<?php include('nav-top1.php'); ?>
<div class="wrapper">
</br>
</br>
</br>
</br>
</br>
</br>
</br>
<div id="element" class="hero-body-index">
<div class="alert alert-info">
<p><font color=""><h2>Login</h2></font></p>
Enter the details to login your account
</div>
<hr>
<form method="POST" >
<table>
<tr><td><font color="">UserName:</font> </td><td><input type="text" name="UserName" class="UserName_hover"></td></tr>
<tr><td>...<td></tr>
<tr><td><font color="">Password:</font> </td><td><input type="Password" name="Password" class="Password_hover"></td></tr>
<tr><td>...<td></tr>
<tr><td></td><td> <button class="btn btn-primary btn-large" name="Login"><i class="icon-ok-sign icon-large"></i> Login</button></td></tr>
<tr><td>
</td><tr>
</form>
</table>
</br>
<div class="error">
<?php
if (isset($_POST['Login'])){
$UserName=$_POST['UserName'];
$Password=$_POST['Password'];
$login_query=mysql_query("select * from user where UserName='$UserName' and Password='$Password' and User_Type='Admin'");
$count=mysql_num_rows($login_query);
$login_query1=mysql_query("select * from user where UserName='$UserName' and Password='$Password' and User_Type='User'");
$count1=mysql_num_rows($login_query1);
$row1=mysql_fetch_array($login_query1);
$f=$row1['FirstName'];
$l=$row1['LastName'];
$row=mysql_fetch_array($login_query);
$f=$row['FirstName'];
$l=$row['LastName'];
if ($count1 == 1){
session_start();
$_SESSION['id']=$row1['User_id'];
$_SESSION['User_Type']=$row1['User_Type'];
$type=$row1['User_Type'];
mysql_query("INSERT INTO history (data,action,date,user)VALUES('$f $l', 'Login', NOW(),'$type')")or die(mysql_error());
header('location:home_user.php');
}
if ($count > 0){
session_start();
$_SESSION['id']=$row['User_id'];
$_SESSION['User_Type']=$row['User_Type'];
$type=$row['User_Type'];
mysql_query("INSERT INTO history (data,action,date,user)VALUES('$f $l', 'Login', NOW(),'$type')")or die(mysql_error());
header('location:home.php');
}else{
?>
<div class="alert alert-error">
<button class="close" data-dismiss="alert">Ч</button>
Please check your UserName and Password
</div>
<?php }
}
?>
</div>
</div>
</br>
</br>
</br>
</br>
</br>
</br>
</br>
<?php include('footer.php');?>
</div>
</body>
</html>
回答by piers
At the point you call session_start()your script has already sent the HTTP headers, making it to late for you to modify them. session_start()should be called before you make any output to the browser. The same goes for header(). To solve this simply put the function calls before you output any HTML, i.e. at the top of your file.
在您调用session_start()脚本时，您的脚本已经发送了 HTTP 标头，因此修改它们为时已晚。session_start()应该在向浏览器进行任何输出之前调用。也是如此header()。要解决这个问题，只需将函数调用放在输出任何 HTML 之前，即放在文件的顶部。
Further reading: https://stackoverflow.com/a/8028987/4261029
回答by Ruddy Lodonou Oke
put session_start(); in first linebefore any html output
把 session_start(); 在任何 html 输出之前的第一行
avoidscalling session_start in your controls.
避免在您的控件中调用 session_start。
whether your page uses sessions then you place it first in your code, or your page does not use sessions.
无论您的页面使用会话，然后将其放在代码中，还是您的页面不使用会话。
try this
尝试这个
<?php
/**
* your dbcon.php must contain only fonctions
* no oupout
*/
include('dbcon.php');
?>
<body>
<?php include('header.php'); ?>
<?php include('nav-top1.php'); ?>
<div class="wrapper">
</br>
</br>
</br>
</br>
</br>
</br>
</br>
<div id="element" class="hero-body-index">
<div class="alert alert-info">
<p><font color=""><h2>Login</h2></font></p>
Enter the details to login your account
</div>
<hr>
<form method="POST" >
<table>
<tr><td><font color="">UserName:</font> </td><td><input type="text" name="UserName" class="UserName_hover"></td></tr>
<tr><td>...<td></tr>
<tr><td><font color="">Password:</font> </td><td><input type="Password" name="Password" class="Password_hover"></td></tr>
<tr><td>...<td></tr>
<tr><td></td><td> <button class="btn btn-primary btn-large" name="Login"><i class="icon-ok-sign icon-large"></i> Login</button></td></tr>
<tr><td>
</td><tr>
</form>
</table>
</br>
<div class="error">
<?php
if (isset($_POST['Login'])){
$UserName=$_POST['UserName'];
$Password=$_POST['Password'];
$login_query=mysql_query("select * from user where UserName='$UserName' and Password='$Password' and User_Type='Admin'");
$count=mysql_num_rows($login_query);
$login_query1=mysql_query("select * from user where UserName='$UserName' and Password='$Password' and User_Type='User'");
$count1=mysql_num_rows($login_query1);
$row1=mysql_fetch_array($login_query1);
$f=$row1['FirstName'];
$l=$row1['LastName'];
$row=mysql_fetch_array($login_query);
$f=$row['FirstName'];
$l=$row['LastName'];
if ($count1 == 1){
// put this in another file
session_start();
$_SESSION['id']=$row1['User_id'];
$_SESSION['User_Type']=$row1['User_Type'];
$type=$row1['User_Type'];
mysql_query("INSERT INTO history (data,action,date,user)VALUES('$f $l', 'Login', NOW(),'$type')")or die(mysql_error());
header('location:home_user.php');
}
if ($count > 0){
// put this in another file
session_start();
$_SESSION['id']=$row['User_id'];
$_SESSION['User_Type']=$row['User_Type'];
$type=$row['User_Type'];
mysql_query("INSERT INTO history (data,action,date,user)VALUES('$f $l', 'Login', NOW(),'$type')")or die(mysql_error());
header('location:home.php');
}else{
?>
<div class="alert alert-error">
<button class="close" data-dismiss="alert">Ч</button>
Please check your UserName and Password
</div>
<?php }
}
?>
</div>
</div>
</br>
</br>
</br>
</br>
</br>
</br>
</br>
<?php include('footer.php');?>
</div>
</body>
