Maybe in PHP

Maybe.php

class Maybe {

    public function __construct(private $value = null) { }

    public function isNothing(): bool {
        return $this->value === null;
    }

    public function isJust(): bool {
        return !$this->isNothing();
    }

    public function __toString() {
        return $this->isNothing() ? 'Nothing' : "Just(" . var_export($this->value, true) . ")";
    }
    
    public function get() {
        return $this->value;
    }

    // Pointed Maybe
    public static function of($x = null) {
        return new Maybe($x);
    }

    // Functor Maybe
    public function map(callable $fn): Maybe {
        return $this->isNothing() ? $this : Maybe::of($fn($this->value));
    }

    // TODO: add more functional methods here
}