Arrow functions

Arrow functions are shorter than function expressions and automatically capture variables from the containing scope without the need for an explicit use clause.

Basic syntax

fn(param1, param2, …, paramN) => expression
fn(param1, param2, …, paramN) => { statements }

// Empty parameter lists are expressed by a pair of parentheses
fn() => expression
fn() => { statements }

// Return types can be added
fn(param1, param2, …, paramN): returnType => expression
fn(param1, param2, …, paramN): returnType => { statements }

Motivation

Arrow functions allow for shorter and more concise syntax.

$materials->map(function($m) { return $m->length(); });

$materials->map(fn($m) => $m->length());

Typing

As in function expressions, parameters can be typed:

$connect= fn(Uri $uri) => new HttpConnection($uri);

Capturing

Unlike function expressions, variables from the enclosing scope are automatically captured. Note that all variables are captured by value. If you wish to capture by reference, you'll need to use a function expression.

See also

• Hack lambdas: The ==> operator and introduction
• PHP RFC: Arrow functions