# PHP Cheat Sheet: PHP 8.3 and 8.4 Syntax and Functions Source: https://srvscripts.com/guides/php-cheat-sheet/ Updated: 2026-10-09 Publisher: srvScripts (https://srvscripts.com/) **Short answer:** PHP 8.3 and 8.4 are the versions to target in 2026. Use `declare(strict_types=1);`, typed parameters and return types, `match` instead of long `switch` blocks, `fn() =>` arrow functions for short callbacks, enums and readonly properties for data, and `JSON_THROW_ON_ERROR` for JSON. PHP 8.4 adds property hooks, `private(set)` visibility, `array_find()` and `new Foo()->method()` without extra brackets. The tables below cover the syntax you reach for every day. The examples in this PHP cheat sheet were run with PHP 8.4.21 (CLI) on 9 October 2026. Features marked 8.4 do not work on PHP 8.3; everything else runs on both. ## Variables, types and strings | Syntax | What it does | Example | | --- | --- | --- | | $name = "web01"; | Variables start with $; no declaration needed | $port = 8080; | | "…$var…" / '…' | Double quotes interpolate; single quotes are literal | "Host {$name}:{$port}" | | 'db01']; | | $a[] = 4; | Append | $hosts[] = 'web02'; | | [$a, $b] = $pair; | Destructuring, also with keys | ['host' => $h] = $cfg; | | [...$a, ...$b] | Spread arrays into a new one (string keys allowed since 8.1) | $all = [...$web, ...$db]; | | array_map() | Transform each value | array_map(fn($n) => $n * 2, $a) | | array_filter() | Keep matching values; keys are preserved | array_values(array_filter($a)) to reindex | | array_reduce() | Fold to one value | array_reduce($a, fn($c, $i) => $c + $i, 0) | | array_column() | One field from a list of rows, optional key | array_column($users, 'age', 'name') | | in_array($x, $a, true) | Search values; pass true for strict | in_array(3, $ids, true) | | array_key_exists() vs isset() | isset is false when the value is null | array_key_exists('ttl', $cfg) | | array_merge() vs + | Merge overwrites string keys; + keeps the left value | $cfg + $defaults | | sort, rsort, asort, ksort, usort | Sort in place (asort/ksort keep keys) | ksort($cfg); | | array_slice(), array_chunk(), array_unique() | Slice, batch, de-duplicate | array_chunk($ids, 100) | | array_is_list() | True for keys 0, 1, 2… in order | array_is_list([1, 2]) | ## Control flow and match | Syntax | What it does | Example | | --- | --- | --- | | if / elseif / else | Conditionals | if ($code >= 500) { … } | | match | Expression with strict comparison, no fall-through, returns a value | see below | | switch | Loose comparison, needs break | Legacy code | | foreach ($a as $k => $v) | Iterate an array or iterable | foreach ($cfg as $key => $val) | | for, while, do … while | Classic loops | for ($i = 0; $i < 3; $i++) | | break / continue | Leave or skip; break 2 leaves two loops | if ($i === 1) continue; | | ?: and ? : | Short ternary and ternary | $user = $input ?: 'guest'; | ``` $label = match (true) { $code >= 500 => 'server error', $code >= 400 => 'client error', default => 'ok', }; echo match ($code) { 200, 204 => 'fine', 404 => 'not found', default => 'other' }; ``` A `match` with no matching arm and no `default` throws `UnhandledMatchError` instead of silently returning null. ## Functions, closures and arrow functions | Syntax | What it does | Example | | --- | --- | --- | | function f(int $n): string | Typed parameters and return | function greet(string $name): string | | $x = "Hello" in the signature | Default value | function greet(string $n, string $g = "Hello") | | Named arguments | Pass by name, in any order | greet(greeting: "Hi", name: "Ann") | | int ...$nums | Variadic parameter | total(...[4, 5]) unpacks an array | | ?int, int|string | Nullable and union types | function f(?int $n): int|string | | void, never, static | No return value / never returns / late static binding | function fail(): never { throw … } | | function () use ($x) {} | Closure; captures by value (use (&$x) by reference) | $mul = function ($n) use ($f) { … }; | | fn($n) => $n * $f | Arrow function: one expression, captures automatically | array_map(fn($n) => $n * $f, $a) | | strlen(...) | First-class callable from any function or method | $len = strlen(...); | | array &$arr | Pass by reference | function addOne(array &$arr): void | Add `declare(strict_types=1);` as the first statement of a file to stop PHP coercing `"5"` into `int` for calls made from that file; a mismatch then throws `TypeError`. ## Classes, enums and readonly properties ``` enum Status: string { case Active = 'active'; case Suspended = 'suspended'; public function label(): string { return ucfirst($this->value); } } final class Server { public function __construct( public readonly string $host, private int $port = 22, ) {} public function dsn(): string { return "{$this->host}:{$this->port}"; } } $s = new Server('db01', 3306); echo $s->dsn(); // db01:3306 echo Status::from('active')->label(); // Active var_dump(Status::tryFrom('x')); // NULL ``` | Feature | Syntax | Note | | --- | --- | --- | | Constructor promotion | public function __construct(private int $port) {} | Declares and assigns in one place | | Readonly property | public readonly string $host | Set once, inside the class; writing again throws Error | | Readonly class | readonly class Point { … } | Every property is readonly (8.2+) | | Enum | enum Suit { case Hearts; } | Suit::Hearts->name, Suit::cases() | | Backed enum | enum Status: string | from() throws on bad input, tryFrom() returns null | | Interface, abstract, trait | interface, abstract class, use Logs; | Traits copy methods into a class | | Nullsafe operator | $user?->profile?->email | Returns null instead of an error on null | | Static factory | public static function local(): static | new static(…) respects subclasses | ## What is new in PHP 8.3 and 8.4 | Version | Feature | Example | | --- | --- | --- | | 8.3 | Typed class constants | const string VERSION = '1.0'; | | 8.3 | Dynamic class constant fetch | Cfg::{$name} | | 8.3 | #[\Override] attribute | Error if the parent has no such method | | 8.3 | json_validate() | Check JSON without decoding it | | 8.3 | str_increment(), mb_str_pad() | str_increment('a9') gives b0 | | 8.3 | DateMalformedStringException | Thrown by new DateTimeImmutable('nonsense') | | 8.4 | Property hooks | get and set logic on the property itself (below) | | 8.4 | Asymmetric visibility | public private(set) int $logins = 0; | | 8.4 | new without wrapping brackets | new Server('h1', 1)->dsn() | | 8.4 | array_find(), array_find_key(), array_any(), array_all() | array_find($a, fn($n) => $n > 4) | | 8.4 | mb_trim(), mb_ucfirst() | Multibyte-safe trim and capitalise | | 8.4 | #[\Deprecated] | Mark your own functions as deprecated | ``` class User { public string $email { set(string $value) { if (!str_contains($value, '@')) throw new ValueError('bad email'); $this->email = strtolower($value); } } public string $domain { get => substr($this->email, strpos($this->email, '@') + 1); } } $u = new User; $u->email = 'Ann@Example.COM'; echo $u->email, ' ', $u->domain; // ann@example.com example.com ``` PHP 8.4 also deprecates implicitly nullable parameters such as `function f(string $s = null)`. Write `?string $s = null` instead. ## Errors and exceptions | Syntax | What it does | Example | | --- | --- | --- | | try / catch / finally | Handle exceptions; finally always runs | see below | | catch (A | B $e) | Catch several types | catch (InvalidArgumentException | TypeError $e) | | Throwable | Parent of Exception and Error | catch (\Throwable $e) in a top-level handler | | TypeError, ValueError, DivisionByZeroError | Engine errors (extend Error, not Exception) | intdiv(1, 0) | | class ConfigError extends RuntimeException {} | Your own exception type | throw new ConfigError("missing DB_HOST"); | | $e->getMessage(), getCode(), getTraceAsString() | Details for logging | error_log($e->getMessage()); | ``` try { throw new InvalidArgumentException('bad port', 22); } catch (InvalidArgumentException | TypeError $e) { echo $e->getMessage(), ' ', $e->getCode(); } finally { echo "cleanup\n"; } ``` ## Files, JSON and the command line | Task | Code | | --- | --- | | Read a whole file | $txt = file_get_contents('/etc/hostname'); | | Lines as an array | file($path, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES) | | Stream a large file | while (($line = fgets($fh)) !== false) { … } | | Append with a lock | file_put_contents($log, $msg, FILE_APPEND | LOCK_EX); | | Decode JSON safely | json_decode($s, true, flags: JSON_THROW_ON_ERROR) | | Encode readable JSON | json_encode($a, JSON_PRETTY_PRINT | JSON_THROW_ON_ERROR) | | Dates | (new DateTimeImmutable('now', new DateTimeZone('UTC')))->format(DATE_ATOM) | | Environment | getenv('DB_HOST') | **For server admins:** most PHP problems on a hosting server are configuration, not code. These CLI commands answer the usual questions: | Command | What it shows | | --- | --- | | php -v | Version of the CLI binary (on cPanel, /opt/cpanel/ea-php84/root/usr/bin/php -v for a specific EA4 version) | | php -l file.php | Syntax check without running the file | | php --ini | Which php.ini and extra .ini files are loaded | | php -m | Compiled and loaded extensions | | php -i | grep memory_limit | One setting as the CLI sees it | | php -r 'echo PHP_VERSION, "\n";' | Run one line of code | | php -S 127.0.0.1:8000 -t public/ | Built-in development server (never for production) | The CLI and the web server can use different PHP versions and different php.ini files. To see what a site really runs, put `