HTTP协议是一种无状态协议，这意味着你对网站的每一个请求都是独立的，而且因此无法通过它自身保存数据。但这种简单性也是它在互联网早期就广泛传播的原因之一。
不过，它仍然有一种方法能让你用cookies的形式来保存请求之间的信息。这种方法使你能够更有效率的进行会话管理和维持数据。
有两种处理cookies的方式—服务端(php,asp等)和客户端(javascript).在这个教程中，我们将学习到以php和javascript这两种方式如何去创建cookies。
Cookies and php
setting cookies
在php中创建cookie你需要用到setcookie这个方法。它需要些参数(除了第一个参数是必需的，其它参数都是可选的)
setcookie(
'pageVisits', //cookie名字，必需的
$visited, //cookie的值
time()+7*24*60*60, //过期时间,设置为一个星期
'/', //cookie可用的文件路径
'demo.tutorialzine.com' //cookie绑定的域名
)
如果过期时间设置为0(默认设置也是0)，那么当浏览器重启时cookie将会丢失。
参数'/'表示你域名下所有文件路径cookie都可以用(当然你也可以为它设置单一的文件路径,例：'/admin/')。
你还可以传给个这个函数别两个额外的参数，这里没有给出。它们被规定为boolean类型的。
第一个参数表示cookie仅在一个安全的HTTPS连接才运转,而第二个参数表示不能使用javascript操作cookie。
对大多数人来说，你只需要第四个参数，剩下的就忽略了。
reading cookies
用php读取cookie就简单多了。所有的传给脚本的cookies都在$_COOKIE这个超级全局数组里。
在我们的例子里，可以用下面的代码来读取cookies:
$visits = (int)$_COOKIE['pageVisits']+1;
echo "You visited this site: ".$visits." times";
值得注意的地方是,当下一个页面加载好时，也可以用$_COOKIE来取得你用setcookie方法设置的cookies,
你应该意识到了什么。
deleting cookies
为了删除cookies，仅仅需要用setcookie函数为cookies设置一个已经过去时间做为过期就行了。
setcookie(
'pageVisits',
$visited,
time()-7*24*60*60, //设置为前一个星期，cookie将会被删除
'/',
'demo.tutorialzine.com'
)
Cookies and jQuery
在jquery中使用cookies，你需要一个插件Cookie plugin.
Setting cookies
用Cookie plug-in设置cookies是很直观的:
$(document).ready(function(){
// Setting a kittens cookie, it will be lost on browser restart:
$.cookie("kittens","Seven Kittens");
// Setting demoCookie (as seen in the demonstration):
$.cookie("demoCookie",text,{expires: 7, path: '/', domain: 'demo.tutorialzine.com'});
// "text" is a variable holding the string to be saved
});
Reading cookies
读取cookie甚至更简单，只需要调用$.cookie()方法，给它一个cookie-name就可以了,这个方法会返回cookie的值:
$(document).ready(function(){
// Getting the kittens cookie:
var str = $.cookie("kittens");
// str now contains "Seven Kittens"
});
Deleting cookies
删除cookie，只需要在次使得$.cookie()方法,把第二个参数设置为null就可以了。
$(document).ready(function(){
// Deleting the kittens cookie:
var str = $.cookie("kittens",null);
// No more kittens
});
完整例子：
demo.php
<?php
// Always set cookies before any data or HTML are printed to the page
$visited = (int)$_COOKIE['pageVisits'] + 1;
setcookie( 'pageVisits', // Name of the cookie, required
$visited, // The value of the cookie
time()+7*24*60*60, // Expiration time, set for a week in the future
'/', // Folder path, the cookie will be available for all scripts in every folder of the site
'demo.tutorialzine.com'); // Domain to which the cookie will be locked
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>MicroTut: Getting And Setting Cookies With jQuery & PHP | Tutorialzine demo</title>
<link rel="stylesheet" type="text/css" href="styles.css" mce_href="styles.css" />
<mce:script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" mce_src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></mce:script>
<mce:script type="text/javascript" src="jquery.cookie.js" mce_src="jquery.cookie.js"></mce:script>
<mce:script type="text/javascript"><!--
$(document).ready(function(){
var cookie = $.cookie('demoCookie');
// If the cookie has been set in a previous page load, show it in the div directly:
if(cookie) $('.jq-text').text(cookie).show();
$('.fields a').click(function(e){
var text = $('#inputBox').val();
// Setting a cookie with a seven day validity:
$.cookie('demoCookie',text,{expires: 7, path: '/', domain: 'demo.tutorialzine.com'});
$('.jq-text').text(text).slideDown('slow');
e.preventDefault();
});
$('#form1').submit(function(e){ e.preventDefault(); })
})
// --></mce:script>
</head>
<body>
<h1>MicroTut: Getting And Setting Cookies With jQuery & PHP</h1>
<h2>Go Back <a href="http://tutorialzine.com/2010/03/microtut-getting-setting-cookies-jquery-php/" mce_href="http://tutorialzine.com/2010/03/microtut-getting-setting-cookies-jquery-php/">To The Tutorial »</a></h2>
<div class="section">
<div class="counter"><?php echo $visited?></div>
<p>The number above indicates how many times you've visited this page (PHP cookie). Reload to test.</p>
</div>
<div class="section">
<div class="jq-text"></div>
<form action="" method="get" id="form1">
<div class="fields">
<input type="text" id="inputBox" />
<a href="">Save</a>
</div>
</form>
<p>Write some text in the field above and click Save. It will be saved between page reloads with a jQuery cookie.</p>
</div>
</body>
</html>
jquery.cookie.js
/**
* Cookie plugin
*
* Copyright (c) 2006 Klaus Hartl (stilbuero.de)
* Dual licensed under the MIT and GPL licenses:
* http://www.opensource.org/licenses/mit-license.php
* http://www.gnu.org/licenses/gpl.html
*
*/
/**
* Create a cookie with the given name and value and other optional parameters.
*
* @example $.cookie('the_cookie', 'the_value');
* @desc Set the value of a cookie.
* @example $.cookie('the_cookie', 'the_value', { expires: 7, path: '/', domain: 'jquery.com', secure: true });
* @desc Create a cookie with all available options.
* @example $.cookie('the_cookie', 'the_value');
* @desc Create a session cookie.
* @example $.cookie('the_cookie', null);
* @desc Delete a cookie by passing null as value. Keep in mind that you have to use the same path and domain
* used when the cookie was set.
*
* @param String name The name of the cookie.
* @param String value The value of the cookie.
* @param Object options An object literal containing key/value pairs to provide optional cookie attributes.
* @option Number|Date expires Either an integer specifying the expiration date from now on in days or a Date object.
* If a negative value is specified (e.g. a date in the past), the cookie will be deleted.
* If set to null or omitted, the cookie will be a session cookie and will not be retained
* when the the browser exits.
* @option String path The value of the path atribute of the cookie (default: path of page that created the cookie).
* @option String domain The value of the domain attribute of the cookie (default: domain of page that created the cookie).
* @option Boolean secure If true, the secure attribute of the cookie will be set and the cookie transmission will
* require a secure protocol (like HTTPS).
* @type undefined
*
* @name $.cookie
* @cat Plugins/Cookie
* @author Klaus Hartl/[email protected]
*/
/**
* Get the value of a cookie with the given name.
*
* @example $.cookie('the_cookie');
* @desc Get the value of a cookie.
*
* @param String name The name of the cookie.
* @return The value of the cookie.
* @type String
*
* @name $.cookie
* @cat Plugins/Cookie
* @author Klaus Hartl/[email protected]
*/
jQuery.cookie = function(name, value, options) {
if (typeof value != 'undefined') { // name and value given, set cookie
options = options || {};
if (value === null) {
value = '';
options.expires = -1;
}
var expires = '';
if (options.expires && (typeof options.expires == 'number' || options.expires.toUTCString)) {
var date;
if (typeof options.expires == 'number') {
date = new Date();
date.setTime(date.getTime() + (options.expires * 24 * 60 * 60 * 1000));
} else {
date = options.expires;
}
expires = '; expires=' + date.toUTCString(); // use expires attribute, max-age is not supported by IE
}
// CAUTION: Needed to parenthesize options.path and options.domain
// in the following expressions, otherwise they evaluate to undefined
// in the packed version for some reason...
var path = options.path ? '; path=' + (options.path) : '';
var domain = options.domain ? '; domain=' + (options.domain) : '';
var secure = options.secure ? '; secure' : '';
document.cookie = [name, '=', encodeURIComponent(value), expires, path, domain, secure].join('');
} else { // only name given, get cookie
var cookieValue = null;
if (document.cookie && document.cookie != '') {
var cookies = document.cookie.split(';');
for (var i = 0; i < cookies.length; i++) {
var cookie = jQuery.trim(cookies[i]);
// Does this cookie string begin with the name we want?
if (cookie.substring(0, name.length + 1) == (name + '=')) {
cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
break;
}
}
}
return cookieValue;
}
};
styles.css
*{
margin:0;
padding:0;
}
body{
/* Setting default text color, background and a font stack */
color:#555555;
font-size:0.825em;
background: #fcfcfc;
font-family:Arial, Helvetica, sans-serif;
}
.section{
margin:0 auto 60px;
text-align:center;
width:600px;
}
.counter{
color:#79CEF1;
font-size:180px;
}
.jq-text{
display:none;
color:#79CEF1;
font-size:80px;
}
p{
font-size:11px;
padding:0 200px;
}
form{
margin-bottom:15px;
}
input[type=text]{
border:1px solid #BBBBBB;
color:#444444;
font-family:Arial,Verdana,Helvetica,sans-serif;
font-size:14px;
letter-spacing:1px;
padding:2px 4px;
}
/* The styles below are only necessary for the styling of the demo page: */
h1{
background:#F4F4F4;
border-bottom:1px solid #EEEEEE;
font-size:20px;
font-weight:normal;
margin-bottom:15px;
padding:15px;
text-align:center;
}
h2 {
font-size:12px;
font-weight:normal;
padding-right:40px;
position:relative;
right:0;
text-align:right;
text-transform:uppercase;
top:-48px;
}
a, a:visited {
color:#0196e3;
text-decoration:none;
outline:none;
}
a:hover{
text-decoration:underline;
}
.clear{
clear:both;
}
h1,h2,p.tutInfo{
font-family:"Myriad Pro",Arial,Helvetica,sans-serif;
}
结束语:
关于cookie的使用，你需要注意的是不要把一些敏感信息(例如用户名、密码)保存在cookies中，
为因当每一个页面加载时cookies都会和headers一样传递到页面，很容易被不法份子截取到。
但是，只要有适当的预防措施，你就可以用这个简单的技术实现大量的互动。