Microsoft Word - Core PHP Programming Using PHP to Build Dynamic Web Sites

print("VALUE=\"Try It\">\n");

print("\n");

print("\n");
print("\n");
?>

Cookies

Cookies are small strings of data created by a Web server but stored on the client. In
addition to having names and values, cookies have an expiration time. Some are set to
last for only a matter of minutes. Others persist for months. This allows sites to recognize
you without requiring a password when you return. To learn more about cookies, you
may wish to visit Netscape's site
<http://developer.netscape.com/docs/manuals/communicator/jsguide4/cookies.htm

.

Using cookies with PHP is almost as easy as using form fields. Any cookies passed from
the browser to the server are converted automatically into variables. In addition, cookies
are stored in the HTTP_COOKIE_VARS array.

If you wish to send a cookie, you use the setcookie function, described in Chapter 8. A
cookie is sent to the browser as a header. Just like other headers, you must set cookies
before sending any content. When you do set a cookie, the browser may refuse to accept
it. Many people turn off cookies. So, you cannot count on the cookie being present the
next time a user requests a page.

Setting a cookie does not create a variable—not immediately. When setting a cookie, you
are asking the browser to store information that it will return when it next requests a
page. Subsequent page requests will cause the cookie to be created as a variable for your
use. If you write a script that requires the cookie variable always be set, set it
immediately after sending the cookie.

Cookies are a sensitive topic. Some people view them as intrusive. You are asking
someone to store information on their computer, although each cookie is limited in size.
My advice with cookies is to keep them minimal. In most cases it is practical to use a
single cookie for your entire site. If you can identify that user with a unique ID, you can
use that ID to look up information you know about them, such as preferences. Keep in
mind that each page load causes the browser to send the cookie. Imagine an extreme case
where you have created ten 1K cookies. That's 10K of data the browser must send with
each page request.

File Uploads

A file upload is a special case of getting form input. Half of the story is putting together
the correct HTML. File uploads are specified in RFC 1867. They are supported by
Netscape Navigator 2 and above, as well as Internet Explorer 4 and above. Placing an