要訪問PHP中的cookie數(shù)據(jù)，需使用$_COOKIE超全局數(shù)組，該數(shù)組以鍵值對形式存儲瀏覽器隨當前請求發(fā)送的所有cookie。讀取時應先用isset()檢查是否存在，如$_COOKIE['user']；注意cookie僅在頁面刷新后可用，且其作用域受路徑、域名及安全標志影響。常見錯誤包括設置后立即訪問、拼寫錯誤、未檢查存在性及誤認為cookie安全可靠。若需存儲多個值，可使用json_encode編碼存儲，并在讀取時解碼驗證數(shù)據(jù)。

To access cookie data in PHP, you use the $_COOKIE superglobal array. This array holds all the cookies sent by the browser with the current request. Each cookie is stored as a key-value pair, where the key is the cookie name and the value is its content.

How to Read a Cookie

Once a cookie has been set — either by your own code using setcookie() or by another script — you can access it using $_COOKIE['cookie_name'].

For example:

if (isset($_COOKIE['user'])) {
    echo 'Welcome back, ' . $_COOKIE['user'];
} else {
    echo 'New visitor';
}

A few things to note:

• Always check if a cookie exists using isset() before trying to access it.
• Cookie values are strings; if you need other types, you'll have to convert them manually.
• Cookies are only available after the page reloads — setting one doesn't make it appear in $_COOKIE immediately.

Understanding Cookie Scope

Cookies are not always available everywhere on your site. Their availability depends on how they were set:

• Path: A cookie set with setcookie('user', 'John', '/', ...) will be available throughout the entire domain.
• Domain: If you're working with subdomains, you might need to specify the domain like .example.com.
• Secure & HttpOnly flags: These don’t affect $_COOKIE, but they do impact security and accessibility from JavaScript.

If a cookie isn't showing up in $_COOKIE, double-check the path and domain used when it was created.

Common Mistakes When Accessing Cookies

It's easy to run into issues if you're not careful. Here are some common pitfalls:

• ? Trying to access a cookie right after setting it — remember, it’s only available on the next request.
• ? Using incorrect names or misspelling the cookie key.
• ? Not checking whether the cookie exists first with isset() or array_key_exists().
• ? Assuming cookies are secure — they’re client-side and can be manipulated.

Also, keep in mind that browsers may block third-party cookies depending on privacy settings, especially in cross-site contexts.

Handling Multiple Cookie Values

Sometimes, you may want to store more than a single value in a cookie. Since cookies can only hold strings, you’ll need to serialize or structure the data yourself.

One approach is to store JSON-encoded data:

// Setting multiple values
$data = ['user' => 'John', 'role' => 'editor'];
setcookie('userdata', json_encode($data), time() 3600, '/');

// Reading it back
if (isset($_COOKIE['userdata'])) {
    $userData = json_decode($_COOKIE['userdata'], true);
    echo 'User role: ' . $userData['role'];
}

Just remember to decode and validate the data each time you read it.

That's basically it for accessing cookies via $_COOKIE. It's straightforward once you understand how cookies are stored and retrieved. Just watch out for timing, scope, and data format — those are the most common gotchas.

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