PHP 8: new features & how it compares to older versions

PHP 8.0 is a major release with new syntax, a JIT compiler, and a stricter type system. Here are the highlights that change day-to-day code, plus notes on upgrading WordPress projects.

1. The JIT compiler

Normally PHP compiles to opcodes run on a virtual machine. The just-in-time compiler can emit native machine code and run it directly on the CPU. It's a big win for CPU-heavy, math-style workloads — but for typical I/O-bound web apps the difference is modest. It's off by default.

2. Nullsafe operator

Chain calls without manual null checks:

// Before
$country = null;
if ($session !== null) {
  $user = $session->user;
  if ($user !== null) {
    $address = $user->getAddress();
    if ($address !== null) {
      $country = $address->country;
    }
  }
}

// PHP 8
$country = $session?->user?->getAddress()?->country;

3. Named arguments

Pass arguments by name and skip optional ones:

htmlspecialchars($string, double_encode: false);

4. Union types

Declare more than one type natively instead of in docblocks:

public function setId(int|string $id): void {}

5. Constructor property promotion

Less boilerplate for value objects:

// PHP 8
class Comment {
  public function __construct(
    public string $title,
    public string $body,
  ) {}
}

6. Match expression

Like switch, but an expression, with strict comparison and no fall-through:

$result = match($status) {
  200, 201 => 'success',
  404 => 'not found',
  default => 'unknown',
};

7. Attributes

Structured, native metadata in place of docblock annotations:

#[Route('/api/users', methods: ['GET'])]
public function list() {}

WordPress compatibility

WordPress core runs on PHP 8, but plugins and themes are the risk. Many older plugins use patterns PHP 8 now treats more strictly (e.g. passing null where a string is expected, or removed/changed functions). Test on a staging site, enable debugging, and update plugins before moving production.

Deprecations to watch

• Stricter type juggling — some loose comparisons changed behavior.
• Several long-deprecated functions and the @-silenced fatal patterns no longer behave the same.
• Always run your test suite and PHPCS against the 8.0 ruleset before upgrading.

Overall PHP 8 makes code shorter and safer — well worth the upgrade once your dependencies are ready.