Syntax: $arrow = fn($x) => $x + $y; Variables automatically captured *by-value* Shorter prefix: %fn% Implicit return is *one* expression Great for filter: $this->existingSchemaPaths = array_filter($paths, function ($v) use ($names) { return in_array($v, $names); }); Becomes: $this->existingSchemaPaths = array_filter($paths, fn($v) => in_array($v, $names));