Master PHP.
Variables, Types, Strings & Output.

<?php
// 1. Valid variable declarations
$username = "Shubh";
$_sessionToken = "auth_token_98765";
$userAge = 22;           // camelCase (Standard PSR-12)
$user_email = "shubh@xlab.xyz"; // snake_case

// 2. Case-sensitivity demonstration
$city = "San Francisco";
$City = "Tokyo";
$CITY = "Berlin";

echo "city: $city | City: $City | CITY: $CITY\n";

// 3. Dynamic typing (Type changes upon re-assignment)
$data = 42;             // Initially integer
var_dump($data);

$data = "Now a String"; // Changed to string
var_dump($data);
?>

<?php
// ============================================================================
// 1. GLOBAL SCOPE & ACCESSING VIA global / $GLOBALS
// ============================================================================
$appName = "PHP Masterclass";
$version = "8.3";

function showAppDetails() {
    // METHOD A: Using the 'global' keyword
    global $appName;
    
    // METHOD B: Using the superglobal $GLOBALS array
    $ver = $GLOBALS['version'];
    
    echo "App: $appName (v$ver)\n";
}

showAppDetails();

// ============================================================================
// 2. LOCAL SCOPE ISOLATION
// ============================================================================
function testLocal() {
    $localVar = "I live only inside testLocal()";
}
testLocal();
// echo $localVar; // Warning: Undefined variable $localVar!

// ============================================================================
// 3. STATIC VARIABLE PERSISTENCE ACROSS CALLS
// ============================================================================
function countHits() {
    static $hits = 0; // Initialized once only
    $hits++;
    echo "Visit Count: $hits\n";
}

countHits(); // Output: Visit Count: 1
countHits(); // Output: Visit Count: 2
countHits(); // Output: Visit Count: 3
?>

<?php
// 1. Basic Variable Variable
$key = "author";
$$key = "Shubh"; // Creates $author = "Shubh"

echo "Value of \$key    : " . $key . "\n";
echo "Value of \$\$key   : " . $$key . "\n";
echo "Value of \$author : " . $author . "\n\n";

// 2. Real-World Use Case: Dynamic Request Parameter Binding
$requestData = [
    'title' => 'PHP 8 Master Guide',
    'rating' => 4.9,
    'tags' => 'backend, web, development'
];

foreach ($requestData as $field => $value) {
    $$field = $value; // Dynamically creates $title, $rating, and $tags!
}

echo "Extracted Title  : $title\n";
echo "Extracted Rating : $rating ⭐\n";
echo "Extracted Tags   : $tags\n";
?>

<?php
// 1. Defining constants
define("SITE_NAME", "PHP Masterclass with Shubh");
define("DB_PORT", 3306);
const MAX_UPLOAD_LIMIT_MB = 100;

echo "Site: " . SITE_NAME . " | Max Upload: " . MAX_UPLOAD_LIMIT_MB . "MB\n\n";

// 2. Using Magic Constants
echo "Current File Line : " . __LINE__ . "\n";
echo "Current Directory : " . __DIR__ . "\n";
echo "Current File Path : " . __FILE__ . "\n";

function trackExecution() {
    echo "Running inside function: " . __FUNCTION__ . "() on line " . __LINE__ . "\n";
}

trackExecution();
?>

<?php
// 1. Explicit Type Casting
$rawPrice = "99.50 USD";
$priceFloat = (float)$rawPrice;
$priceInt = (int)$rawPrice;

var_dump($priceFloat); // float(99.5)
var_dump($priceInt);   // int(99)

// 2. Type Checking Functions
$score = "100";
if (is_numeric($score)) {
    echo "\$score is valid numeric data!\n";
}

// 3. Array to Object Casting
$userArray = ["id" => 42, "name" => "Shubh"];
$userObj = (object)$userArray;

echo "User Object Property: " . $userObj->name . "\n";

// 4. Strict Typing Example
// declare(strict_types=1); enforces exact parameter and return types:
function calculateTotal(int $quantity, float $price): float {
    return $quantity * $price;
}

echo "Total: $" . calculateTotal(3, 19.99) . "\n";
?>

<?php
// 1. Modifying by reference in foreach
$scores = [80, 90, 100];
foreach ($scores as &$score) {
    $score += 5; // Adds bonus 5 points to each
}
unset($score); // Break reference to prevent bugs!
print_r($scores); // [85, 95, 105]

// 2. Modern Array Destructuring with keys
$book = ['title' => 'Clean Code', 'author' => 'Robert Martin', 'year' => 2008];
['title' => $title, 'author' => $author] = $book;
echo "Book: $title by $author
";

// 3. Array Spread Unpacking
$frontend = ['HTML', 'CSS', 'JS'];
$backend = ['PHP', 'MySQL'];
$fullstack = [...$frontend, ...$backend, 'Docker'];
print_r($fullstack);
?>

<?php
// 1. Associative sorting preserving keys
$salaries = ["Carol" => 75000, "Alice" => 95000, "Bob" => 60000];
asort($salaries); // Sort by salary ascending while keeping names
print_r($salaries);

// 2. Custom multidimensional sort using the spaceship operator (<=>)
$users = [
    ["name" => "Shubh", "age" => 22],
    ["name" => "Alex",  "age" => 30],
    ["name" => "John",  "age" => 25]
];

usort($users, fn($a, $b) => $a['age'] <=> $b['age']); // Sort by age ascending
print_r($users);
?>

<?php
$products = [
    ["name" => "Laptop", "price" => 1200, "in_stock" => true],
    ["name" => "Mouse",  "price" => 25,   "in_stock" => false],
    ["name" => "Desk",   "price" => 350,  "in_stock" => true]
];

// 1. array_filter: Keep only items in stock
$inStock = array_filter($products, fn($p) => $p['in_stock']);

// 2. array_map: Extract uppercase product names with 10% tax
$formatted = array_map(fn($p) => [
    'item' => strtoupper($p['name']),
    'total_with_tax' => $p['price'] * 1.10
], $inStock);

// 3. array_reduce: Calculate grand total inventory value
$grandTotal = array_reduce($inStock, fn($sum, $p) => $sum + $p['price'], 0);

print_r($formatted);
echo "Grand Total Inventory: $" . number_format($grandTotal, 2) . "
";
?>

<?php
// 1. Default Parameters & Pass by Reference (&$value)
function applyDiscount(float &$price, float $percentage = 10.0): void {
    $price -= ($price * ($percentage / 100));
}

$itemPrice = 100.00;
applyDiscount($itemPrice, 20.0); // Directly alters $itemPrice
echo "Discounted Price: $itemPrice
";

// 2. Named Arguments (PHP 8)
function createUser(string $name, string $role = "Subscriber", bool $isActive = true): string {
    return "User: $name | Role: $role | Active: " . ($isActive ? 'Yes' : 'No');
}

// Skips $role and specifies $isActive directly:
echo createUser(name: "Shubh", isActive: true) . "
";
?>

<?php
// 1. Anonymous Closure with 'use' to capture parent scope
$taxRate = 0.18;
$calculateTotal = function(float $subtotal) use ($taxRate): float {
    return $subtotal + ($subtotal * $taxRate);
};
echo "Closure Total: $" . $calculateTotal(100.00) . "
";

// 2. Concise Arrow Function (auto-captures $taxRate by value)
$calcArrow = fn(float $subtotal): float => $subtotal * (1 + $taxRate);
echo "Arrow Function Total: $" . $calcArrow(200.00) . "
";

// 3. First-Class Callable Syntax (PHP 8.1+)
$funcRef = strtoupper(...);
echo $funcRef("learn php with shubh") . "
";
?>

<?php
class User {
    // PHP 8 Constructor Property Promotion:
    // Declares visibility + data type directly in constructor arguments!
    public function __construct(
        public readonly int $id,
        public string $name,
        private string $email,
        protected string $role = "Developer"
    ) {}

    public function getDetails(): string {
        return "User #{$this->id}: {$this->name} ({$this->role}) - Email: {$this->email}";
    }

    public function setEmail(string $newEmail): void {
        if (filter_var($newEmail, FILTER_VALIDATE_EMAIL)) {
            $this->email = $newEmail;
        }
    }
}

$user = new User(101, "Shubh", "shubh@xlab.xyz", "Lead Architect");
echo $user->getDetails() . "
";
echo "Accessing Public Property: " . $user->name . "
";
?>

<?php
// Contract Interface
interface PaymentGatewayInterface {
    public function charge(float $amount): bool;
}

// Concrete Implementation 1
class StripeGateway implements PaymentGatewayInterface {
    public function charge(float $amount): bool {
        echo "Processing $amount via Stripe API...
";
        return true;
    }
}

// Concrete Implementation 2
class PayPalGateway implements PaymentGatewayInterface {
    public function charge(float $amount): bool {
        echo "Processing $amount via PayPal Gateway...
";
        return true;
    }
}

// Polymorphic Processor
function checkout(PaymentGatewayInterface $gateway, float $total) {
    $gateway->charge($total);
}

checkout(new StripeGateway(), 199.99);
checkout(new PayPalGateway(), 49.50);
?>

<?php
trait LoggableTrait {
    public function log(string $message): void {
        echo "[" . date('Y-m-d H:i:s') . "] LOG: $message
";
    }
}

class OrderService {
    use LoggableTrait; // Injects log() method horizontally

    public function createOrder(int $orderId) {
        $this->log("Order #$orderId successfully placed.");
    }
}

$service = new OrderService();
$service->createOrder(98765);
?>

<?php
$host = 'localhost';
$db   = 'php_masterclass';
$user = 'root';
$pass = 'secure_password';
$charset = 'utf8mb4';

// 1. Data Source Name (DSN)
$dsn = "mysql:host=$host;dbname=$db;charset=$charset";

// 2. Recommended PDO Configuration Options
$options = [
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION, // Throw exceptions on errors
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,       // Return associative arrays
    PDO::ATTR_EMULATE_PREPARES   => false,                  // Native prepared statements
];

try {
    $pdo = new PDO($dsn, $user, $pass, $options);
    echo "Connected to MySQL successfully via PDO!
";
} catch (PDOException $e) {
    die("Database Connection Error: " . $e->getMessage());
}
?>

<?php
// ============================================================================
// 1. CREATE (INSERT) WITH NAMED PLACEHOLDERS (:name, :email)
// ============================================================================
$stmt = $pdo->prepare("INSERT INTO users (name, email, role) VALUES (:name, :email, :role)");
$stmt->execute([
    ':name'  => 'Shubh',
    ':email' => 'shubh@xlab.xyz',
    ':role'  => 'Admin'
]);
$userId = $pdo->lastInsertId();
echo "Inserted User ID: $userId
";

// ============================================================================
// 2. READ (SELECT) WITH PARAMETER BINDING
// ============================================================================
$stmt = $pdo->prepare("SELECT id, name, email FROM users WHERE role = :role LIMIT :limit");
$stmt->bindValue(':role', 'Admin', PDO::PARAM_STR);
$stmt->bindValue(':limit', 10, PDO::PARAM_INT);
$stmt->execute();
$admins = $stmt->fetchAll(); // Returns all rows as assoc array
print_r($admins);

// ============================================================================
// 3. UPDATE RECORD & CHECK ROW COUNT
// ============================================================================
$updateStmt = $pdo->prepare("UPDATE users SET name = :name WHERE id = :id");
$updateStmt->execute([':name' => 'Shubh (Verified)', ':id' => $userId]);
echo "Rows Updated: " . $updateStmt->rowCount() . "
";

// ============================================================================
// 4. DELETE RECORD SAFELY
// ============================================================================
$delStmt = $pdo->prepare("DELETE FROM users WHERE id = :id");
$delStmt->execute([':id' => $userId]);
echo "Deleted User #$userId successfully.
";
?>

<?php
try {
    // 1. Begin atomic transaction
    $pdo->beginTransaction();

    $fromAccountId = 1;
    $toAccountId   = 2;
    $transferAmount = 250.00;

    // Step A: Deduct from Sender
    $stmt1 = $pdo->prepare("UPDATE accounts SET balance = balance - :amt WHERE id = :id");
    $stmt1->execute([':amt' => $transferAmount, ':id' => $fromAccountId]);

    // Step B: Credit to Receiver
    $stmt2 = $pdo->prepare("UPDATE accounts SET balance = balance + :amt WHERE id = :id");
    $stmt2->execute([':amt' => $transferAmount, ':id' => $toAccountId]);

    // 2. Commit transaction if both succeeded
    $pdo->commit();
    echo "Funds transferred successfully!
";

} catch (Exception $e) {
    // 3. Rollback changes if anything failed
    $pdo->rollBack();
    echo "Transaction failed and rolled back: " . $e->getMessage() . "
";
}
?>