如果我使用session_start两次，请替换会话['msg']？错误：会话已启动

Question

我在我的 students.php

上方会出现错误

已经启动了一个会话 - 忽略Session_start((

我有一个CRUD，其中我必须通知用户是否已更新，删除或创建。

CRUD工作正常，但是，如果我在server.php中删除session_start()，则不会显示该通知。

suduss.php：

<?php if (isset($_SESSION['msg'])): ?>
<div class="msg">
  <?php 
      echo $_SESSION['msg'];
      unset($_SESSION['msg']);
  ?>

server.php

if(!isset($_SESSION)) 
{ 
  session_start(); 
} 
...
$_SESSION['msg'] = "New student saved";
header('location: students.php'); //redirect back to page
$_SESSION['msg'] = "Information updated";
header('location: students.php'); //redirect back to page

redirect.php

<?php
session_start(); 
if (!isset($_SESSION['username']))
{
header('location: login.php');
die();
}
?>

我应该将var $_SESSION['msg']更改为另一个变量吗？我是PHP的总初学者，对不起，如果这可能是一个愚蠢的问题。

Answer 1

看起来您没有一个框架，所以我认为有一些一般提示可以帮助您的脚本成功。

1(在您的网站root中有一个顶级配置文件，您在所有主要页面的顶部都包含该文件：

/config.php

<?php
# Create some helpful constants
define('ROOT_DIR',__DIR__);
define('DS',DIRECTORY_SEPARATOR);
define('FUNCTIONS',ROOT_DIR.DS.'functions');
define('BASE_URL','http://www.example.com');
# This includes our function loader (see below)
include_once(FUNCTIONS.DS.'loadFunc.php');
# Load the getSession() function (see below)
loadFunc('getSession');
# Start session here
session_start();

2(然后创建一些有用的函数(我将学习面向对象的编程，以便您可以有效地使用框架，但是功能总比没有好(：

/functions/loadfunc.php

function loadFunc($name)
{
    if(!is_array($name))
        $name = array($name);
    foreach($name as $func) {
        # If the function is already loaded, skip
        if(function_exists($func))
            continue;
        # See if the function file exists
        if(is_file($file = FUNCTIONS.DS.$func.'.php'))
            include_once($file);
        }
    }
}

/functions/getsession.php

function getSession($key=false,$clear=false)
{
    # If requesting a specific value return that
    if(!empty($key)) {
        # Get value
        $value = (isset($_SESSION[$key]))? $_SESSON[$key] : false;
        # If the key is set and clear is set, clear the value
        if(isset($_SESSON[$key]) && $clear) {
            unset($_SESSON[$key]);
        }
        # Return session value
        return $value;
    }
    # No key set, return full session
    return $_SESSION;
}

/functions/setsession.php

function setSession($key,$value)
{
    $_SESSION[$key] = $value;
}

/functions/redirect.php

function redirect($to,$exit=true)
{
    header("Location: {$to}");
    # You should exit on redirect
    if($exit)
        exit;
}

3(现在，当您进入创建页面时，您将此配置在页面顶部包含：

/Students.php

<?php
# Now that you include this, you know session is always set
include(__DIR__.DIRECTORY_SEPARATOR.'config.php');
# Get the key msg from the session and use parameter #2 to clear the session key
$msg = getSession('msg',true);
# It's not empty, write message
if($msg): ?>
<div class="msg">
  <?php echo $msg ?>
</div>
<?php endif ?>

/server.php

<?php
# Include config
include(__DIR__.DIRECTORY_SEPARATOR.'config.php');
# Load our two required functions
loadFunc(array('setSession','redirect'));
# You have to determine either message here, not both.
# Using pseudo-code here to demonstrate
if($add) {
    # Use function to set session value
    setSession('msg',"New student saved");
}
elseif($update) {
    setSession('msg',"Information updated");
}
# Since both use the same redirect, you only need it once
redirect('students.php');

因此，如果您在所有文件中删除所有session_start()，除了配置外，然后始终在顶部的顶级页面上包含配置，您将不会遇到会话错误。

。