PHP Cookies - Explaing PHP Cookie with example

In the course of developing highly interactive web sites it is necessary to deal with large amount of data flow between client browswer and web server. It is quite cumbersome handling such large amount of data using hidden fiels in HTML forms. This problem can be overcomed by using HTTP cookies. HTTP cookies are the bunch of data/text sent by the server to the web browswer. Web browser store this data locally and send back to the server each time it accesses the server before it expires. Note that now a days Most browsers allow users choice to accept cookies or not, sometime rejection causes web site to not work properly.

setcookie() function.
This function in PHP Language is used to work with HTTP cookies. setcookie() defines a cookie to be sent along with the rest of the HTTP headers. This must be called before sending any output to the browser because cookies are part of the HTTP header. On successful it will return TRUE. But this does not mean that client browser has ccepted cookie.

setcookie() syntax.

bool setcookie ( string name [, string value [, int expire [, string path [, string domain [, int secure]]]]])

• name: This argument sets the name of the cookie.
  for example

  setcookie(‘mycookie’, …)

  will set mycookie and is called $_COOKIE['mycookie'] at server side.
• value: This will set the value of the cookie. Since this values is stored on the client browser extra care must be taken that it does not store some secure information e.g passwords. The values is accessed by $_COOKIE['mycookie'] at the web server.
• expire: Sets the expire time of cookie. It is Unix timestamp so generally it is used with time() function. For example time()+60*30. This will set the cookie to expire in 30 minutes. If not set the cookie is not persistent and will expire when the browser closes.
• path: The path of cookies are used to organise cookies based on the path at web server. If set to ‘/’ this cookie is availabe to all directories. If set to ‘/dir1/’ this cookie is availabe to dir1 only and all sub directories of /dir1 i.e /dir1/sub1. Note that the default value is the current directory so if the current directory is ‘/dir1/’ and you want to set it for all directories it must be ‘/’
• domain: This argument will decide in which domain cookie is accesible. Value ‘www.mydomin.com’
  makes it accesible to www sub-domain only. To make it accessible to all subdomains of mydomin.com a value
  ‘.mydomin.com’ must be set.
• secure: Value 1 indicates the cookie must be used on secure (https) connection. Default value is 0.

setcookie() Examples.

setcookie(‘mycookie’, ‘Test mycookie’);\\This will set ‘mycookie’ with value ‘Test mycookie’ will expire when browser closes.

setcookie(‘mycookie’, ‘Test mycookie’, time()+3600*24); \\ This will expire in 1 day.

setcookie(‘mycookie’, ‘Test mycookie’, time()+3600*24, “/dir1/”); \\Available to /dir1 directory and all subdirectories under it.

Accessing cookie values at server.
At server in PHP script, cookies sent from the client browser will be turned into PHP variables. After PHP 4.1.0 the global array variable $_COOKIE is set for cookies from the client. $HTTP_COOKIE_VARS is also present which is availabe before PHP 4.1.0. See example below.
echo $_COOKIE["mycookie"]; This will output “Test mycookie” in our example.

Testing cookie.
On successful return of setcookie() does not mean that client browser has accepted the cookie or cookie is set successfully. It must be checked on next loading of the page if a cookie was successfully set or not. This can be done by using PHP function print_r($_COOKIE) function. This will show weather the cookie is set or not.

Deleting a cookie.
Cookies can be deleted by setting its value to “” and all other parameters must be the same as they were set at the time of sending the cookie. We must ensure that the expiration date is in the past when deleting the cookie. See examples below.

setcookie (“mycookie”, “”, time() – 3600);
setcookie (“mycookie”, “”, time() – 3600, “/dir1/”);

Multiple cookies.
Multiple cookies can be set using following.

setcookie(‘mycookie1′, ‘Test mycookie1′);
setcookie(‘mycookie2′, ‘Test mycookie2′);
setcookie(‘mycookie3′, ‘Test mycookie3′);
setcookie(‘mycookie4′, ‘Test mycookie4′);

And can be accessed by following.

echo $_COOKIE["mycookie1"];
echo $_COOKIE["mycookie2"];
echo $_COOKIE["mycookie3"];
echo $_COOKIE["mycookie4"];

Cookies Array.
We can use PHP array in cookies. see example below

setcookie(“mycookie[0]“, “value1″);
setcookie(“mycookie[1]“, “value2″);
setcookie(“mycookie1['one']“, “value11″);
setcookie(“mycookie1['five']“, “value15″);

This is similar of setting many cookies but the values are placed in the PHP array at the
receing PHP script.

foreach ($_COOKIE['mycookie'] as $key => $value) {
  echo “$key:$value “;
  }
//This will print 0:value1 1:value2 And
foreach ($_COOKIE['mycookie1'] as $key => $value) {
  echo “$key:$value “;
  }

Will print print one:value11 five:value15