关于在php中session_start（）的具体解释？有了解的吗？

Question

（函数解释和说明）

Answer 1

session_start
(PHP 4, PHP 5)

session_start — Initialize session data

说明
bool session_start ( void )

session_start() creates a session or resumes the current one based on the current session id that's being passed via a request, such as GET, POST, or a cookie.

If you want to use a named session, you must call session_name() before calling session_start().

session_start() will register internal output handler for URL rewriting when trans-sid is enabled. If a user uses ob_gzhandler or like with ob_start(), the order of output handler is important for proper output. For example, user must register ob_gzhandler before session start.

返回值
This function always returns TRUE.

更新日志

版本 说明
4.3.3 As of now, calling session_start() while the session has already been started will result in an error of level E_NOTICE. Also, the second session start will simply be ignored.

范例

例 2126. A session example: page1.php

<?php
// page1.php

session_start();

echo 'Welcome to page #1';

$_SESSION['favcolor'] = 'green';
$_SESSION['animal'] = 'cat';
$_SESSION['time'] = time();

// Works if session cookie was accepted
echo '<br /><a href="page2.php">page 2</a>';

// Or maybe pass along the session id, if needed
echo '<br /><a href="page2.php?' . SID . '">page 2</a>';
?>

After viewing page1.php, the second page page2.php will magically contain the session data. Read the session reference for information on propagating session ids as it, for example, explains what the constant SID is all about.

例 2127. A session example: page2.php

<?php
// page2.php

session_start();

echo 'Welcome to page #2<br />';

echo $_SESSION['favcolor']; // green
echo $_SESSION['animal']; // cat
echo date('Y m d H:i:s', $_SESSION['time']);

// You may want to use SID here, like we did in page1.php
echo '<br /><a href="page1.php">page 1</a>';
?>

注释
注意: If you are using cookie-based sessions, you must call session_start() before anything is outputted to the browser.

Answer 2

很简单
在您把用户信息存储到 PHP session 中之前，首先必须启动会话。session_start（）就是启动session 的意思 一般写的文件开头

Answer 3

session 是缓存而已只不过他的值是存到服务器端的。
如果想要使用session不能直接 $_SESSION['NAME']='张三'，
在用session之前需要先开启session 。于是就用到了session_start（）方法。
这时候在使用 $_SESSION['NAME']='张三'的时候才有效。
（补充：只要定义了session的内容，所有php文件中只要开启了session都可以使用。）