What is a Cookie?
A cookie is a text-only string of information that a website transfers to the cookie file of the browser on your computer's hard disk so that a website can remember who you are.
A cookie will typically contain the name of the domain from which the cookie has come, the "lifetime" of the cookie, and a value, usually a randomly generated unique number. Two types of cookies are used on this website-session cookies, which are temporary cookies that remain in the cookie file of your browser until you leave the site, and persistent cookies, which remain in the cookie file of your browser for much longer (though how long will depend on the lifetime of the specific cookie).
Are All Cookies the Same?
There are two different types of cookies:
Session cookies - these are temporary and are erased when you close your browser at the end of your surfing session. The next time you visit that particular site it will not recognise you and will treat you as a completely new visitor as there is nothing in your browser to let the site know that you have visited before. These will be called 'PHPSESSID'
Persistent cookies - these remain on your hard drive until you erase them or they expire. How long a cookie remains on your browser depends on how long the visited website has programmed the cookie to last.
What Are Session Cookies Used For?
Without cookies, websites and their servers have no memory. A cookie, like a key, enables swift passage from one place to the next. Without a cookie every time you open a new web page the server where that page is stored will treat you like a completely new visitor.
Websites typically use session cookies to ensure that you are recognised when you move from page to page within one site and that any information you have entered is remembered. For example, if an e-commerce site did not use session cookies then items placed in a shopping basket would disappear by the time you reach the checkout. You can choose to accept session cookies by changing the settings in your browser.
What Are Persistent Cookies Used For?
A persistent cookie enables a website to remember you on subsequent visits, speeding up or enhancing your experience of services or functions offered.
For example, a website may offer its contents in different languages. On your first visit, you may choose to have the content delivered in French and the site may record that preference in a persistent cookie set on your browser. When you revisit that site it will use the cookie to ensure that the content is delivered in French. The "Remember Me" function on a website sets these kind of cookies.
What Can't Cookies Do?
Tutorial by Raduce
Online (last 15 mins): zlay