What you have to know about the meaning and usage of COOKIE in PHP

1. What is a cookie?

Cookies are created on the server side and written back to the client browser.

After receiving the instruction, the browser creates a cookie file in the local temporary folder, which stores your client browser. Every time you visit a website, it will detect whether there is cookie information for the website. If If there are, they will also be sent at the same time.

Note: Cookie content is stored in key/value pairs, and both keys and values ​​can only be strings.

Function function setcookie(key, value, validity period)Set session cookie parameters

Define cookie

//setcookie(键，值，有效期[秒])
setcookie("name","lisi",time()+1000);  //如果不设置有效期，关闭浏览器就会消失
setcookie("pwd","111",time()+7*24*3600); //有效期为7天

Delete cookie data (set expiration time to invalidate cookie )

setcookie("name","lisi",time()-1);   //1、设置有效期为过去的某一个时间
setcookie("name",false,time()-1);    //2、设置cookie的值为false
setcookie("name","",time()-1);       //2、设置cookie的值为空
//3、清理浏览器缓存：在浏览器里清理缓存

2. Create

Use the setcookie method in php to create cookies.

<?php
    $se=setcookie("name","lisi",time()+30*60,"/");
    var_dump($se);
 ?>

3. Use

to use the $_COOKIE global variable in php to obtain cookie data.

<?php
    $user=$_COOKIE["name"]; //获取name值
    var_dump($user);
?>

4. Destruction

There is no direct destruction method in PHP. The expiration time of the cookie is usually reset.

<?php
    $user=setcookie("name",null,time()+1,"/");
    var_dump($user);
?>

Summary of COOKIE:

• COOKIE is stored on the client side, which is relatively unsafe.

• The data type stored in COOKIE can only be strings.

• The data capacity stored by COOKIE can only store approximately 4KB of data.

• The browser can disable the cache or disable COOKIE, then the COOKIE function will be invalid.

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