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Cookies

A cookie is a small value a site asks a browser to store. The browser sends the value back with later requests, so PHP can read it from the $_COOKIE array.

setcookie hands back true

setcookie takes a cookie name and a value. The var_dump line shows the call handed back true.

<?php
var_dump(setcookie("user", "Hana"));

A saved name reads back

A real request would fill $_COOKIE before the program runs. This program fills the array by hand, in the same shape.

<?php
$_COOKIE["user"] = "Hana";
echo "Hello " . $_COOKIE["user"] . "\n";

A returning visitor and a first visit

isset tests whether the user key sits in $_COOKIE. The program removes the key with unset, then tests the same array again.

<?php
$_COOKIE["user"] = "Hana";
if (isset($_COOKIE["user"])) {
  echo "Welcome back, " . $_COOKIE["user"] . "\n";
} else {
  echo "First visit\n";
}
unset($_COOKIE["user"]);
if (isset($_COOKIE["user"])) {
  echo "Welcome back, " . $_COOKIE["user"] . "\n";
} else {
  echo "First visit\n";
}

Example

<?php
$_COOKIE["user"] = "Hana";
$_COOKIE["theme"] = "dark";
echo "Hello " . $_COOKIE["user"] . "\n";
echo "Theme: " . $_COOKIE["theme"] . "\n";

Key points

  • Use setcookie to ask the browser to store a cookie under a name.
  • The setcookie call in the first snippet hands back true.
  • The browser stores the cookie after the response reaches it.
  • On a later request, the browser sends stored cookies to the server.
  • PHP fills $_COOKIE with the cookies sent in a request.
  • A command line run holds no browser, so it cannot store cookies between runs.

In this example, two lines fill $_COOKIE by hand with a user name and a theme. The greeting line reads the user key. The theme line reads the theme key and prints dark.

Note

The hand-filled $_COOKIE values in this lesson show one program viewing one request.

Try it Yourself

Edit the code, then press Run.

Running is simulated

Exercise

What does var_dump(setcookie("user", "Hana")) print in the first snippet?