What is the First-Class Callables syntax (...) in PHP 8.1, and how does it improve callbacks?

Short answer

It converts any function or method directly into a Closure object with (...) without passing unsafe strings or arrays.

Explanation

Previously, passing a method as a callback required an array or string, such as [$this, 'handleMethod'] or 'strlen'. PHP 8.1 added First-Class Callable syntax: strlen(...) or $this->handleMethod(...). The engine immediately creates a Closure and checks that the function exists and is valid, while also supporting IDE autocomplete.

Code example

$numbers = ["10", "20", "30"];
// Modern syntax
$integers = array_map(intval(...), $numbers);

Common mistakes

• Using legacy function-name strings in modern applications, preventing static analysis tools from catching typos.

Follow-up questions

• What are Attributes in PHP 8+, and how are they better than older PHPDoc annotations?

Sources

• PHP docs — First-class callable syntax