PHP Cookies

A cookie is a small piece of data that your website stores in the browser of the visitor. The browser sends it back to your server with every request. Cookies are used to remember things like a language choice, a theme, or a login (usually with a session).

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Create a cookie

Use the setcookie() function. It must be called before any output, because cookies are sent in the HTTP headers. From PHP 7.3 you can pass the options as an array.

<?php
setcookie("username", "Robin", [
    "expires"  => time() + 3600,   // 1 hour from now
    "path"     => "/",
    "secure"   => true,            // send only over HTTPS
    "httponly" => true,            // JavaScript can not read it
    "samesite" => "Lax"
]);

echo "Cookie is set.";
?>

Output:

Option	Meaning
expires	When the cookie ends, as a time stamp. If you skip it, the cookie is deleted when the browser closes
path	The part of the site where the cookie is available. “/” means the whole site
secure	Send only on HTTPS
httponly	Hide the cookie from JavaScript (protects from theft by XSS)
samesite	Controls sending with requests from other sites (Lax or Strict). Helps against CSRF

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Read a cookie

A cookie is not available in the same request that sets it. It is available from the next page load, in the $_COOKIE array.

<?php
if (isset($_COOKIE["username"])) {
    echo "Welcome back, " . htmlspecialchars($_COOKIE["username"]);
} else {
    echo "Hello, new visitor";
}
?>

Output:

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Delete a cookie

To delete a cookie, set it again with a time in the past. Use the same path as when you created it.

<?php
setcookie("username", "", time() - 3600, "/");
?>

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Important points

• The user can see, change and delete cookies. Never trust a cookie value, and never store a password or private data in it.
• A cookie can hold only about 4 KB of data.
• Cookies can be disabled by the user, so your site should work without them for basic things.
• Many countries need a consent from the visitor for cookies that are not essential.

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Exercises & Assignments
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Interview Questions & Answers
Difference Between Cookies and Session