Optional.php

<?php

class Optional
{
	private $value;

	public function __construct($value)
	{
		$this->value = $value;
	}

	public function map(callable $func)
	{
		if (null === $this->value) {
			return $this;
		}

		$result = $func($this->value);

		return new Optional($result);
	}
	
	public function flatMap(callable $func)
	{
		if (null === $this->value) {
			return $this;
		}
		
		return $func($this->value);
	}
}