PHP
Syntax, Types & OOP
PHP: Syntax, Types & OOP PHP is a server-side scripting language designed for web development. PHP 8.x introduced JIT compilation, union types, fibers, readonly…
PHP: Syntax, Types & OOP
PHP is a server-side scripting language designed for web development. PHP 8.x introduced JIT compilation, union types, fibers, readonly properties, and many modern language features that rival Python and Ruby.
Core Syntax
<?php
// Variables (dynamically typed)
$name = "Alice";
$age = 30;
$price = 9.99;
$active = true;
$nothing = null;
// String interpolation
echo "Hello, $name! You are $age years old.\n";
echo "Item costs {$item->price} USD\n"; // complex expressions need braces
echo 'No $interpolation here'; // single quotes = literal
// Heredoc / Nowdoc
$sql = <<<EOT
SELECT *
FROM users
WHERE name = '$name'
EOT;
$literal = <<<'EOT'
No $interpolation in nowdoc
EOT;
// Type juggling & casting
$num = (int) "42px"; // 42
$str = (string) 3.14; // "3.14"
$bool = (bool) ""; // false
$arr = (array) "hello"; // ["hello"]
// Strict comparison
var_dump(0 == "a"); // true (loose) — avoid
var_dump(0 === "a"); // false (strict) — prefer
// Null coalescing
$username = $_GET['user'] ?? 'Guest';
$config['timeout'] ??= 30; // assign if null
// Spread operator
$args = [1, 2, 3];
function sum(int ...$nums): int { return array_sum($nums); }
sum(...$args);Arrays
// Indexed array
$fruits = ['apple', 'banana', 'cherry'];
$fruits[] = 'date'; // append
$fruits[0] = 'avocado'; // update
count($fruits); // 4
array_push($fruits, 'elderberry');
$last = array_pop($fruits);
array_unshift($fruits, 'first');
$first = array_shift($fruits);
// Associative array (like a map/dict)
$user = [
'name' => 'Alice',
'age' => 30,
'roles' => ['admin', 'editor'],
];
$user['email'] = 'alice@example.com';
isset($user['phone']); // false
// Array functions
sort($arr); // sort indexed (modifies in place)
rsort($arr); // reverse sort
asort($arr); // sort by value, preserve keys
ksort($arr); // sort by key
array_map(fn($x) => $x * 2, $arr);
array_filter($arr, fn($x) => $x > 0);
array_reduce($arr, fn($carry, $item) => $carry + $item, 0);
in_array('banana', $fruits); // true/false
array_key_exists('name', $user); // true/false
array_keys($user); // ['name', 'age', 'roles', 'email']
array_values($user);
array_merge($arr1, $arr2);
array_slice($arr, 1, 3); // offset 1, length 3
array_splice($arr, 1, 2, ['x']); // remove 2, insert 'x' at pos 1
array_unique($arr); // remove duplicates
array_flip($arr); // swap keys and values
array_column($users, 'email'); // extract column from 2D arrayOOP
<?php
// Modern PHP class
class User
{
public function __construct(
private readonly int $id,
private string $name,
private string $email,
private array $roles = [],
) {}
public function getName(): string { return $this->name; }
public function rename(string $name): void
{
if (strlen($name) < 2) {
throw new \InvalidArgumentException("Name too short");
}
$this->name = $name;
}
public function hasRole(string $role): bool
{
return in_array($role, $this->roles, strict: true);
}
public function withRole(string $role): static // covariant return
{
$clone = clone $this;
$clone->roles[] = $role;
return $clone;
}
public function toArray(): array
{
return ['id' => $this->id, 'name' => $this->name, 'email' => $this->email];
}
// Magic methods
public function __toString(): string { return $this->name; }
public function __get(string $prop): mixed { return $this->$prop ?? null; }
}
// Interface + abstract class
interface Notifiable {
public function notify(string $message): void;
}
abstract class BaseModel {
abstract public function validate(): bool;
public function save(): void {
if ($this->validate()) {
// save to DB
}
}
}
// Traits (mixins)
trait Timestamps {
private \DateTimeImmutable $createdAt;
public function initTimestamps(): void {
$this->createdAt = new \DateTimeImmutable();
}
public function getCreatedAt(): \DateTimeImmutable {
return $this->createdAt;
}
}
// Enums (PHP 8.1+)
enum Status: string {
case Active = 'active';
case Inactive = 'inactive';
case Pending = 'pending';
public function label(): string {
return match($this) {
Status::Active => 'Active',
Status::Inactive => 'Inactive',
Status::Pending => 'Awaiting Review',
};
}
}
$status = Status::Active;
$status->value; // 'active'
$status->label(); // 'Active'
Status::from('pending'); // Status::Pending