Check if a cookie exists in PHP

Posted on Sep 26, 2022

Learn how you can check if a cookie exists in PHP

Photo from Unsplash

To check if a cookie exists in PHP, you need to call the isset() function on the $_COOKIE array variable.

For example, suppose you want to check for a cookie named lang. You need to call the isset() function inside an if statement as shown below:

// ๐Ÿ‘‡ check if cookie exists
if (isset($_COOKIE["lang"])) {
    print "lang cookie value: " . $_COOKIE["lang"];
} else {
    print "lang cookie doesn't exists";
}

Keep in mind that a cookie can only be accessed after the page has been reloaded.

This is because cookies are sent as part of the header response when you request a page.

Checking for the cookie existence immediately after setting it with setcookie() will cause PHP to return undefined array key warning:

<?php
if (!isset($_COOKIE["lang"])) {
    setcookie("lang", "ja");
}

// ๐Ÿ‘‡ Warning: Undefined array key "lang"
// until next request
print $_COOKIE["lang"];

?>

If you want to check for the cookie without reloading, then you need to call the setcookie() function and set the $_COOKIE value in the next line.

This way, you can use that cookie without a page reload:

<?php
if (!isset($_COOKIE["lang"])) {
    setcookie("lang", "ja");
    $_COOKIE["lang"] = "ja";
}

// ๐Ÿ‘‡ prints "ja"
print $_COOKIE["lang"];

?>

By setting the $_COOKIE key-value pair manually, you tricked the code to think that the cookie is set.

But this may also introduce a bug since your code thinks that the user has the cookie in the first place.

As an alternative, you can add a fallback value as a variable instead:

if (!isset($_COOKIE["lang"])) {
    setcookie("lang", "ja");
}

$fallback_lang = "en";

// ๐Ÿ‘‡ if lang not set, prints fallback value
print isset($_COOKIE["lang"]) ? $_COOKIE["lang"] : $fallback_lang;

Using the ternary condition as shown above is considered the right approach because it doesnโ€™t trick the code with a made-up cookie.

Now youโ€™ve learned how to check if a cookie exists in PHP. Good job! ๐Ÿ‘

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