Optional container

The purpose of the class is to provide type-level solution for representing optional values. Helps to get rid of null checks and if -> else depth.

$value = null;
if ($obj !== null) {
    $value = $obj->getValue();
} else {
    $value = "b";
}

can be replaced with

$value = Optional::ofNullable($obj)
                   ->map(function () { return $obj -> getValue();})
                   ->orElse("b");