


php uses cookies to implement sessions with users, phpcookie implements sessions
The example in this article describes how PHP uses cookies to implement user sessions. Share it with everyone for your reference. The specific analysis is as follows:
PHP contains many functions that can be used to manage and record user information, including simple cookies and full-scale user sessions. Sessions use technology built into the PHP language that makes saving state as simple as referencing a superglobal variable.
1. Cookie Introduction
We can use cookies with PHP scripts to store some smaller information about the user. A cookie is a small amount of data stored by the user's browser in response to a request from a server or script. Through a user's browser, a single host can request to save 20 cookies. Each cookie contains a name, value and expiration date, as well as host and path information. The size limit for a single cookie is 4KB.
After setting the cookie, only the host making the request can read the data, which ensures that user privacy is respected. In addition, the user can configure his browser to accept or reject all cookie requests through him. Therefore, cookies should be used sparingly and should not be relied upon as an essential element in an environment where the implementation is not designed to warn users.
If a web browser is configured to store cookies, it will retain cookie-based information until the expiration date. If the user uses the browser to browse any page that matches the path and domain of the cookie, it will resend the cookie to the server. Subsequently, a PHP script can access the cookie. The cookie is in the environment variable HTTP_COOKIE or as part of the $COOKIE superglobal variable. We can access them in 3 ways:
echo getenv("HTTP_COOKIE");
echo $_COOKIE["vegetable"];
2. Set a cookie using PHP
We can set a cookie in a PHP script in two ways. First, use the header() function to set the SetCookie header. The Header() function expects a string that will then be included in the header portion of the server response. Since headers are automatically sent for you, header() must be called before the Jehol output is sent to the browser.
Although not difficult, this method of setting a cookie requires us to write a function to build the header string. Formatting dates and URL-encoding name/value pairs like this example is not a particularly difficult task, but it is still a repetitive job because PHP provides a function to do this, which is setcookie().
The Setcookie() function does exactly what its name suggests, it outputs a Set-Cookie header. Therefore, it should be called before any other content is sent to the browser. This function accepts the cookie name, cookie value, expiration date in UNIX timestamp format, path, domain, and an integer that is set to 1 if the cookie is only sent over a secure connection. In addition to the first parameter , all parameters of this function are optional.
if ( isset ( $_COOKIE [ "vegetable" ])){
echo "
Hello again, you have chosen: " . $_COOKIE [ "vegetable" ]. ".
" ;}
else {
echo "
Hello you. This may be your first visit.
" ;}
?>
Even if we set the cookie when the script is first run, the $_COOKIE["vegetable"] variable will not be created at this time. Since a cookie is only read when the browser sends it to the server, we won't be able to read it until the user revisits a page in this domain.
Formally speaking, to delete a cookie, just call setcookies():
with the cookie name parameter. setcookie("vegetable");
However, this approach does not always work and cannot be relied upon. Instead, to delete a cookie, set the cookie with a time that is sure to have expired, which is the safest method:
Setcookie("vegetable", "", time()-60, "/", "yourdomain.com", 0);
Also make sure to pass to setcookie() the same path, domain, and security parameters that were used to initially set the cookie.
3. Overview of session functions
When a visitor accesses a session-enabled page, either a new identifier is assigned, or the user is reassociated with an identifier already established for a previous visit. Any variables that are already associated with the session are available to your code through the $_SESSION superglobal variable.
Session state is usually stored in a temporary file, although you can implement database storage using a function called session_set_save_handler().
4. Start a conversation
echo "
Your session ID is " . session_id (). "
" ;?>
5. Use session variables
Having access to a unique session identifier in every PHP document is just the beginning of session functionality. When a session is started, we can store as many variables as we want in the superglobal variable $_SESSION and then access them on any session-aware page.
The following program adds two variables to the superglobal variable $_SESSION:
$_SESSION [ "product1" ] = "Sonic Screwdriver" ;
$_SESSION [ "product2" ] = "HAL 2000" ;
echo "The products have been registered." ;
?>
The magic of the above program won't be realized until the user moves to a new page. The following program creates a single PHP script that accesses variables stored in the superglobal variable $_SESSION.
echo "Your chosen products are:" ;
echo "
- " ;
- " . $_SESSION [ "product1" ]. " " ;
- " . $_SESSION [ "product2" ]. " " ;
echo "
echo "
echo "
?>
The following program listing creates a form that allows a user to select multiple products. We can use session variables to create a basic shopping cart.
arraysession.php:
?>
Product Choice Page
if ( isset ( $_POST [ "form_products" ])){
if (! empty ( $_SESSION [ "products" ])){
$products = array_unique (
array_merge ( unserialize ( $_SESSION [ "products" ]),
$_POST [ "form_produces" ]));
}
else
{
$_SESSION [ "products" ] = serialize ( $_POST [ "form_products" ]);
}
echo "
Your products have been registered!
" ;}
?>
session1.php:
* Created on 2011-1-19
*
* To change the template for this generated file go to
* Window - Preferences - PHPeclipse - PHP - Code Templates
*/
session_start ();
?>
Content Page
if ( isset ( $_SESSION [ "products" ])){
echo "Your cart:
- " ;
- " . $p . " " ;
foreach ( unserialize ( $_SESSION [ "products" ]) as $p ){
echo "
}
echo "
}
?>
6.在查询字符串中传递会话 ID
7.销毁会话和重置变量
8.在一个带有注册用户的环境中使用会话
希望本文所述对大家的php程序设计有所帮助。

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。


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