Modern PHP Syntax for TS Developers

Overview

Modern PHP (8.0+) has adopted many syntax features that TypeScript/JavaScript developers will recognize. This chapter explores the syntactic similarities and differences, helping you write idiomatic PHP using familiar patterns.

Learning Objectives

By the end of this chapter, you'll be able to:

• ✅ Use arrow functions in PHP (like TypeScript's arrow syntax)
• ✅ Apply null coalescing and nullish coalescing operators
• ✅ Use spread operators for arrays
• ✅ Write match expressions (better than switch)
• ✅ Leverage string interpolation
• ✅ Use named arguments (like object parameters in TS)
• ✅ Destructure arrays (PHP's equivalent to array destructuring)

Code Examples

📁 View Code Examples on GitHub

This chapter includes working examples of modern PHP syntax:

• Arrow functions and closures
• Match expressions
• Spread operators and named arguments
• Array methods and TypeScript-style helpers

Run the examples:

git clone https://github.com/dalehurley/codewithphp.git
cd codewithphp/code/php-typescript-developers/chapter-02
php arrow-functions.php

Arrow Functions

TypeScript

// Arrow function syntax
const double = (x: number): number => x * 2;

// Multi-line arrow function
const greet = (name: string): string => {
  const message = `Hello, ${name}!`;
  return message;
};

// Array methods with arrow functions
const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.map(x => x * 2);
const evens = numbers.filter(x => x % 2 === 0);

PHP (7.4+)

<?php
declare(strict_types=1);

// Arrow function (short syntax - single expression only)
$double = fn(int $x): int => $x * 2;

// Multi-line requires traditional closure
$greet = function(string $name): string {
    $message = "Hello, {$name}!";
    return $message;
};

// Array methods with arrow functions
$numbers = [1, 2, 3, 4, 5];
$doubled = array_map(fn($x) => $x * 2, $numbers);
$evens = array_filter($numbers, fn($x) => $x % 2 === 0);

Key Differences:

Feature	TypeScript	PHP
Keyword	None	fn
Single Expression	✅	✅
Multi-line Body	✅	❌ (use function)
Implicit Return	✅	✅
Auto-capture Variables	✅	✅

Important: PHP arrow functions (fn) can only have a single expression. For multi-line functions, use traditional closures.

Null Coalescing Operators

The ?? Operator (Null Coalescing)

TypeScript:

// Nullish coalescing (??)
const name = user.name ?? "Guest";
const port = config.port ?? 3000;

PHP:

<?php
// Null coalescing (??)
$name = $user['name'] ?? "Guest";
$port = $config['port'] ?? 3000;

// Chain multiple
$value = $a ?? $b ?? $c ?? "default";

Identical behavior! Returns the right operand if the left is null or undefined.

The ??= Operator (Null Coalescing Assignment)

TypeScript:

// Assign only if null/undefined
port ??= 3000;

PHP (7.4+):

<?php
$port ??= 3000; // Only assigns if $port is null or undefined

The ?-> Operator (Optional Chaining)

TypeScript:

// Optional chaining
const city = user?.address?.city;
const firstItem = array?.[0];

PHP (8.0+):

<?php
// Nullsafe operator
$city = $user?->address?->city;
$firstItem = $array[0] ?? null; // No ?. for arrays

PHP Limitation: No optional chaining for arrays—use ?? instead.

Spread Operator

TypeScript

// Array spread
const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const combined = [...arr1, ...arr2]; // [1, 2, 3, 4, 5, 6]

// Object spread
const user = { name: "Alice", age: 30 };
const updatedUser = { ...user, age: 31 };

// Function arguments
function sum(...numbers: number[]): number {
  return numbers.reduce((a, b) => a + b, 0);
}

PHP (7.4+ for arrays, 8.1+ for named args)

<?php
// Array spread (7.4+)
$arr1 = [1, 2, 3];
$arr2 = [4, 5, 6];
$combined = [...$arr1, ...$arr2]; // [1, 2, 3, 4, 5, 6]

// Associative array spread (8.1+)
$user = ['name' => 'Alice', 'age' => 30];
$updatedUser = [...$user, 'age' => 31];

// Function arguments (variadic)
function sum(int ...$numbers): int {
    return array_sum($numbers);
}

sum(1, 2, 3, 4); // 10

PHP Limitation: Spread in associative arrays requires PHP 8.1+.

Match Expression (Better Switch)

TypeScript Switch

function getStatus(code: number): string {
  switch (code) {
    case 200:
      return "OK";
    case 404:
      return "Not Found";
    case 500:
      return "Server Error";
    default:
      return "Unknown";
  }
}

PHP Match (8.0+)

<?php
declare(strict_types=1);

function getStatus(int $code): string {
    return match($code) {
        200 => "OK",
        404 => "Not Found",
        500 => "Server Error",
        default => "Unknown"
    };
}

Benefits of Match over Switch:

• ✅ Returns a value (expression, not statement)
• ✅ Strict comparison (=== by default)
• ✅ No fall-through (no break needed)
• ✅ Exhaustiveness checking

Multiple conditions:

<?php
$result = match($status) {
    200, 201, 202 => "Success",
    400, 404 => "Client Error",
    500, 502, 503 => "Server Error",
    default => "Unknown"
};

String Interpolation

TypeScript

const name = "Alice";
const age = 30;

// Template literals
const message = `Hello, ${name}! You are ${age} years old.`;
const multiline = `
  Line 1
  Line 2
  Line 3
`;

PHP

<?php
$name = "Alice";
$age = 30;

// Double quotes with variable interpolation
$message = "Hello, {$name}! You are {$age} years old.";

// Heredoc (multiline)
$multiline = <<<EOT
Line 1
Line 2
Line 3
EOT;

// Nowdoc (no interpolation, like single quotes)
$nowdoc = <<<'EOT'
Variables like {$name} are not parsed here.
EOT;

Key Differences:

Feature	TypeScript	PHP
Syntax	`${var}`	"{$var}" or "$var"
Quotes	Backticks	Double quotes
Multiline	Native in backticks	Heredoc (<<<EOT)
Expression	`${1 + 1}`	Not directly (use concatenation)

Simple variables can omit braces in PHP:

<?php
$name = "Alice";
echo "Hello, $name!"; // Works
echo "Hello, {$name}!"; // More explicit (recommended)

Named Arguments

TypeScript (Object Parameters)

function createUser({
  name,
  email,
  age = 18,
  isActive = true
}: {
  name: string;
  email: string;
  age?: number;
  isActive?: boolean;
}): User {
  return { name, email, age, isActive };
}

// Call with named parameters
const user = createUser({
  name: "Alice",
  email: "alice@example.com",
  age: 30
});

PHP (8.0+)

<?php
declare(strict_types=1);

function createUser(
    string $name,
    string $email,
    int $age = 18,
    bool $isActive = true
): array {
    return compact('name', 'email', 'age', 'isActive');
}

// Call with named arguments
$user = createUser(
    name: "Alice",
    email: "alice@example.com",
    age: 30
);

// Skip optional parameters
$user2 = createUser(
    name: "Bob",
    email: "bob@example.com",
    isActive: false // Skip $age, use default
);

PHP Named Arguments Benefits:

• ✅ Skip optional parameters
• ✅ Reorder arguments
• ✅ Self-documenting code

Array Destructuring

TypeScript

// Array destructuring
const [a, b, c] = [1, 2, 3];

// Object destructuring
const { name, age } = { name: "Alice", age: 30 };

// Nested destructuring
const { user: { name } } = data;

PHP (7.1+)

<?php
// Array destructuring
[$a, $b, $c] = [1, 2, 3];

// Associative array destructuring
['name' => $name, 'age' => $age] = ['name' => 'Alice', 'age' => 30];

// Nested destructuring
['user' => ['name' => $name]] = $data;

// Skip elements
[, , $third] = [1, 2, 3]; // $third = 3

PHP Limitation: No object destructuring—only arrays.

Property Promotion (Constructor Shorthand)

TypeScript

class User {
  constructor(
    public name: string,
    public email: string,
    private age: number
  ) {}
}

const user = new User("Alice", "alice@example.com", 30);

PHP (8.0+)

<?php
declare(strict_types=1);

class User {
    public function __construct(
        public string $name,
        public string $email,
        private int $age
    ) {}
}

$user = new User("Alice", "alice@example.com", 30);
echo $user->name; // "Alice"

Identical concept! Properties are automatically declared and assigned.

Trailing Comma Support

TypeScript

const arr = [
  1,
  2,
  3, // ✅ Trailing comma allowed
];

function foo(
  a: number,
  b: number, // ✅ Trailing comma allowed
) {}

PHP (7.3+ for arrays, 8.0+ for parameters)

<?php
$arr = [
    1,
    2,
    3, // ✅ Trailing comma allowed
];

function foo(
    int $a,
    int $b, // ✅ Trailing comma allowed (PHP 8.0+)
): void {}

Nullsafe Operator Chain

TypeScript

// Optional chaining
const city = user?.profile?.address?.city;

PHP (8.0+)

<?php
// Nullsafe operator
$city = $user?->profile?->address?->city;

Identical behavior! Returns null if any property in the chain is null.

First-Class Callable Syntax (PHP 8.1+)

TypeScript

class Calculator {
  add(a: number, b: number): number {
    return a + b;
  }
}

const calc = new Calculator();
const addFn = calc.add.bind(calc);
const result = addFn(5, 10); // 15

// Or with arrow function
const addFn2 = (a: number, b: number) => calc.add(a, b);

PHP (8.1+)

<?php
declare(strict_types=1);

class Calculator {
    public function add(int $a, int $b): int {
        return $a + $b;
    }
}

$calc = new Calculator();

// OLD way (verbose)
$addFn = fn($a, $b) => $calc->add($a, $b);

// NEW way (PHP 8.1+): First-class callable
$addFn = $calc->add(...);
$result = $addFn(5, 10); // 15

// Also works with built-in functions
$upperFn = strtoupper(...);
echo $upperFn('hello'); // "HELLO"

// Static methods
$jsonDecodeFn = json_decode(...);

Benefits:

• ✅ Cleaner syntax
• ✅ Works with methods, functions, and static methods
• ✅ Proper type checking

Array Functions Comparison

TypeScript developers coming to PHP often miss familiar array methods. Here's how they translate:

TypeScript Array Methods

const numbers = [1, 2, 3, 4, 5];

// map
const doubled = numbers.map(x => x * 2);

// filter
const evens = numbers.filter(x => x % 2 === 0);

// reduce
const sum = numbers.reduce((acc, x) => acc + x, 0);

// find
const firstEven = numbers.find(x => x % 2 === 0);

// some
const hasEven = numbers.some(x => x % 2 === 0);

// every
const allPositive = numbers.every(x => x > 0);

// includes
const hasThree = numbers.includes(3);

// forEach
numbers.forEach(x => console.log(x));

PHP Array Functions

<?php
$numbers = [1, 2, 3, 4, 5];

// map
$doubled = array_map(fn($x) => $x * 2, $numbers);

// filter
$evens = array_filter($numbers, fn($x) => $x % 2 === 0);

// reduce
$sum = array_reduce($numbers, fn($acc, $x) => $acc + $x, 0);

// find (first match) - no direct equivalent, use loop or array_filter
$firstEven = current(array_filter($numbers, fn($x) => $x % 2 === 0)) ?: null;

// some - no direct equivalent, use loop
$hasEven = count(array_filter($numbers, fn($x) => $x % 2 === 0)) > 0;

// every - no direct equivalent
$allPositive = count(array_filter($numbers, fn($x) => $x > 0)) === count($numbers);

// includes
$hasThree = in_array(3, $numbers, true); // Third param = strict comparison

// forEach
array_walk($numbers, fn($x) => print($x . "\n"));
// Or use regular foreach loop (more idiomatic)
foreach ($numbers as $x) {
    echo $x . "\n";
}

Important Differences:

• PHP's array_map has parameters reversed: array_map(callback, array)
• Use in_array() for checking existence (with strict: true for type-safe)
• No direct find(), some(), every() equivalents—use array_filter() with additional logic
• PHP prefers foreach loops over forEach() method

Modern PHP Array Helper (Custom)

You can create TypeScript-like helpers:

<?php
declare(strict_types=1);

class Arr {
    /**
     * @template T
     * @param array<T> $array
     * @param callable(T): bool $callback
     * @return T|null
     */
    public static function find(array $array, callable $callback): mixed {
        foreach ($array as $item) {
            if ($callback($item)) {
                return $item;
            }
        }
        return null;
    }

    /**
     * @template T
     * @param array<T> $array
     * @param callable(T): bool $callback
     */
    public static function some(array $array, callable $callback): bool {
        foreach ($array as $item) {
            if ($callback($item)) {
                return true;
            }
        }
        return false;
    }

    /**
     * @template T
     * @param array<T> $array
     * @param callable(T): bool $callback
     */
    public static function every(array $array, callable $callback): bool {
        foreach ($array as $item) {
            if (!$callback($item)) {
                return false;
            }
        }
        return true;
    }
}

// Usage
$numbers = [1, 2, 3, 4, 5];
$firstEven = Arr::find($numbers, fn($x) => $x % 2 === 0); // 2
$hasEven = Arr::some($numbers, fn($x) => $x % 2 === 0);   // true
$allPositive = Arr::every($numbers, fn($x) => $x > 0);    // true

Attributes vs Decorators

TypeScript Decorators

// TypeScript decorators (experimental)
function log(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
  const original = descriptor.value;
  descriptor.value = function(...args: any[]) {
    console.log(`Calling ${propertyKey} with`, args);
    return original.apply(this, args);
  };
}

class Calculator {
  @log
  add(a: number, b: number): number {
    return a + b;
  }
}

PHP Attributes (8.0+)

<?php
declare(strict_types=1);

// Define attribute
#[Attribute]
class Route {
    public function __construct(
        public string $path,
        public string $method = 'GET'
    ) {}
}

// Use attribute
class UserController {
    #[Route('/users', 'GET')]
    public function index(): array {
        return ['users' => []];
    }

    #[Route('/users', 'POST')]
    public function store(): array {
        return ['created' => true];
    }
}

// Read attributes via reflection
$reflection = new ReflectionClass(UserController::class);
foreach ($reflection->getMethods() as $method) {
    $attributes = $method->getAttributes(Route::class);
    foreach ($attributes as $attribute) {
        $route = $attribute->newInstance();
        echo "{$route->method} {$route->path} -> {$method->getName()}\n";
    }
}

Differences:

• TypeScript decorators modify behavior at runtime (when supported)
• PHP attributes are metadata only—they don't change behavior automatically
• PHP requires reflection to read attributes
• Common PHP use cases: routing, validation, ORM mapping

Looping Constructs

TypeScript Loops

const items = ['a', 'b', 'c'];

// for...of (values)
for (const item of items) {
  console.log(item);
}

// for...in (keys)
for (const key in items) {
  console.log(key); // "0", "1", "2"
}

// forEach
items.forEach((item, index) => {
  console.log(index, item);
});

// Classic for
for (let i = 0; i < items.length; i++) {
  console.log(items[i]);
}

PHP Loops

<?php
$items = ['a', 'b', 'c'];

// foreach (most common)
foreach ($items as $item) {
    echo $item . "\n";
}

// foreach with index
foreach ($items as $index => $item) {
    echo "{$index}: {$item}\n";
}

// Classic for
for ($i = 0; $i < count($items); $i++) {
    echo $items[$i] . "\n";
}

// while
$i = 0;
while ($i < count($items)) {
    echo $items[$i] . "\n";
    $i++;
}

Associative Arrays (like Objects):

// TypeScript
const user = { name: "Alice", age: 30 };
for (const [key, value] of Object.entries(user)) {
  console.log(`${key}: ${value}`);
}

<?php
// PHP
$user = ['name' => 'Alice', 'age' => 30];
foreach ($user as $key => $value) {
    echo "{$key}: {$value}\n";
}

Union Types in Practice

TypeScript

function format(value: string | number | boolean): string {
  if (typeof value === "string") {
    return value.toUpperCase();
  }
  if (typeof value === "number") {
    return value.toFixed(2);
  }
  return value ? "Yes" : "No";
}

PHP (8.0+)

<?php
declare(strict_types=1);

function format(string|int|float|bool $value): string {
    return match(true) {
        is_string($value) => strtoupper($value),
        is_int($value) || is_float($value) => number_format($value, 2),
        is_bool($value) => $value ? "Yes" : "No",
    };
}

// Or with if/elseif
function formatAlt(string|int|float|bool $value): string {
    if (is_string($value)) {
        return strtoupper($value);
    }
    if (is_int($value) || is_float($value)) {
        return number_format($value, 2);
    }
    return $value ? "Yes" : "No";
}

Match with Truthiness:

• match(true) allows conditional expressions as cases
• More elegant than long if/elseif chains
• Exhaustive by default (must handle all cases)

Practical Comparison Example

Let's build a simple user validator in both languages:

TypeScript

interface User {
  name: string;
  email: string;
  age?: number;
  isActive?: boolean;
}

const validateUser = (user: User): string[] => {
  const errors: string[] = [];

  if (!user.name?.trim()) {
    errors.push("Name is required");
  }

  if (!user.email?.includes("@")) {
    errors.push("Invalid email");
  }

  if ((user.age ?? 0) < 18) {
    errors.push("Must be 18 or older");
  }

  return errors;
};

// Usage
const user = { name: "Alice", email: "alice@example.com", age: 30 };
const errors = validateUser(user);

PHP

<?php
declare(strict_types=1);

class User {
    public function __construct(
        public string $name,
        public string $email,
        public ?int $age = null,
        public bool $isActive = true
    ) {}
}

/**
 * @return array<string>
 */
function validateUser(User $user): array {
    $errors = [];

    if (empty(trim($user->name))) {
        $errors[] = "Name is required";
    }

    if (!str_contains($user->email, "@")) {
        $errors[] = "Invalid email";
    }

    if (($user->age ?? 0) < 18) {
        $errors[] = "Must be 18 or older";
    }

    return $errors;
}

// Usage
$user = new User("Alice", "alice@example.com", 30);
$errors = validateUser($user);

Hands-On Exercise

Task 1: Refactor to Modern PHP

Given this old-style PHP code, refactor it using modern syntax:

<?php
// Old style
function calculateDiscount($price, $discountPercent = 10, $isMember = false) {
    if (!isset($price)) {
        return 0;
    }

    $discount = $isMember ? $discountPercent * 1.5 : $discountPercent;

    switch ($discount) {
        case 10:
            $label = "Standard";
            break;
        case 15:
            $label = "Member";
            break;
        default:
            $label = "Custom";
            break;
    }

    return array(
        'original' => $price,
        'discount' => $discount,
        'final' => $price - ($price * $discount / 100),
        'label' => $label
    );
}

Solution

<?php
declare(strict_types=1);

function calculateDiscount(
    ?float $price,
    float $discountPercent = 10,
    bool $isMember = false
): array {
    $price ??= 0; // Null coalescing assignment

    // Ternary with clear intent
    $discount = $isMember ? $discountPercent * 1.5 : $discountPercent;

    // Match expression (better than switch)
    $label = match($discount) {
        10 => "Standard",
        15 => "Member",
        default => "Custom"
    };

    // Named array keys
    return [
        'original' => $price,
        'discount' => $discount,
        'final' => $price - ($price * $discount / 100),
        'label' => $label
    ];
}

Modern features used:

• Type declarations
• Null coalescing assignment (??=)
• Match expression
• Short array syntax []

Task 2: Convert TypeScript to PHP

Convert this TypeScript function to modern PHP:

const processItems = (items: number[]): { sum: number; avg: number } => {
  const sum = items.reduce((acc, val) => acc + val, 0);
  const avg = sum / items.length;
  return { sum, avg };
};

const numbers = [1, 2, 3, 4, 5];
const result = processItems(numbers);
console.log(`Sum: ${result.sum}, Avg: ${result.avg}`);

Solution

<?php
declare(strict_types=1);

/**
 * @param array<int> $items
 */
function processItems(array $items): array {
    $sum = array_reduce(
        $items,
        fn($acc, $val) => $acc + $val,
        0
    );
    $avg = $sum / count($items);

    return compact('sum', 'avg');
    // Or: return ['sum' => $sum, 'avg' => $avg];
}

$numbers = [1, 2, 3, 4, 5];
$result = processItems($numbers);
echo "Sum: {$result['sum']}, Avg: {$result['avg']}" . PHP_EOL;

Key translations:

• Arrow function → fn($acc, $val) => $acc + $val
• reduce() → array_reduce()
• length → count()
• Template literal → String interpolation with {}

Key Takeaways

1. Arrow functions (fn) support only single expressions; use traditional closures for multi-line
2. Null coalescing (??, ??=) works identically to TypeScript's nullish coalescing
3. Nullsafe operator (?->) is PHP's version of optional chaining (objects only, not arrays)
4. Match expressions are superior to switch: return values, strict comparison, no fall-through
5. Named arguments (PHP 8.0+) allow skipping optional parameters and reordering
6. Property promotion (PHP 8.0+) makes constructors as concise as TypeScript
7. String interpolation uses double quotes "{$var}" instead of backticks `${var}`
8. Spread operator works for arrays; associative array spread requires PHP 8.1+
9. First-class callables (PHP 8.1+): Use fn(...) syntax for cleaner function references
10. Array functions differ: array_map(callback, array) has reversed parameter order vs JS
11. PHP lacks array.find(), array.some(), array.every()—use array_filter() or custom helpers
12. Attributes (PHP 8.0+) are metadata-only, unlike TypeScript decorators that modify behavior
13. foreach is idiomatic in PHP; prefer it over array_walk() for most iterations
14. Union types work great with match(true) for elegant type-based logic

Syntax Cheat Sheet

Feature	TypeScript	PHP
Arrow function	(x) => x * 2	fn($x) => $x * 2
Null coalescing	a ?? b	$a ?? $b
Optional chain	obj?.prop	$obj?->prop
Spread	...arr	...$arr
Match/Switch	switch (x) {}	match($x) {}
String template	`Hello ${x}`	"Hello {$x}"
Named args	foo({ x: 1 })	foo(x: 1)
Destructure	[a, b] = arr	[$a, $b] = $arr

Next Steps

Now that you're familiar with modern PHP syntax, let's dive deeper into functions and closures.

Next Chapter: 03: Functions & Closures: From JS to PHP

Resources

• PHP 8.0 Features
• PHP 8.1 Features
• PHP Arrow Functions RFC
• PHP Match Expression RFC

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