슈퍼전역 변수로 폼 데이터 읽기

<?php
// Safe access with null coalescing
$username = $_POST['username'] ?? '';
$email    = $_POST['email']    ?? '';
$age      = (int) ($_POST['age'] ?? 0);

var_dump($username, $email, $age);

<?php
// URL: /products.php?category=electronics&page=2&sort=price

$category = $_GET['category'] ?? 'all';
$page     = max(1, (int) ($_GET['page'] ?? 1));
$sort     = in_array($_GET['sort'] ?? '', ['price', 'name', 'date'])
            ? $_GET['sort']
            : 'name';

echo "Category: $category, Page: $page, Sort: $sort";

<?php
// HTML: <input type="checkbox" name="newsletter">

$wantsNewsletter = isset($_POST['newsletter']);
// or:
$wantsNewsletter = ($_POST['newsletter'] ?? null) !== null;

echo $wantsNewsletter ? 'Subscribed' : 'Not subscribed';

<!-- HTML -->
<!-- <input type="checkbox" name="tags[]" value="php"> -->
<!-- <input type="checkbox" name="tags[]" value="mysql"> -->

<?php
$tags = $_POST['tags'] ?? [];

if (!is_array($tags)) $tags = [];

foreach ($tags as $tag) {
    echo htmlspecialchars($tag) . PHP_EOL;
}

<?php
echo $_SERVER['REQUEST_METHOD'];   // GET or POST
echo $_SERVER['REQUEST_URI'];       // /page.php?foo=bar
echo $_SERVER['HTTP_HOST'];         // example.com
echo $_SERVER['REMOTE_ADDR'];       // client IP
echo $_SERVER['HTTP_USER_AGENT'];   // browser string

<?php
// Retrieve and validate an integer from POST
$age = filter_input(INPUT_POST, 'age', FILTER_VALIDATE_INT);
if ($age === false) {
    echo 'Invalid age';
}

// Retrieve and sanitize a string from GET
$name = filter_input(INPUT_GET, 'name', FILTER_SANITIZE_SPECIAL_CHARS);
echo $name;

<?php
$email = 'user@example.com';
$ip    = '192.168.1.1';
$url   = 'https://example.com';

var_dump(filter_var($email, FILTER_VALIDATE_EMAIL));  // string
var_dump(filter_var($ip,    FILTER_VALIDATE_IP));     // string
var_dump(filter_var($url,   FILTER_VALIDATE_URL));    // string

<?php
if (isset($_FILES['avatar'])) {
    $file = $_FILES['avatar'];
    
    echo $file['name'];     // original filename: photo.jpg
    echo $file['type'];     // MIME type: image/jpeg
    echo $file['size'];     // bytes: 45231
    echo $file['tmp_name']; // temp path on server
    echo $file['error'];    // 0 = no error
}

<?php
$errors = [];
$name   = '';

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $name = trim($_POST['name'] ?? '');
    if (empty($name)) {
        $errors[] = 'Name is required';
    }
    if (empty($errors)) {
        // process...
        header('Location: /thanks.php');
        exit;
    }
}