Yaml parse fails to understand or allow %YAML

[Dragonrun1]

Directly from the docs at http://www.yaml.org/spec/1.2/spec.html#id2781553
A version 1.2 YAML processor must accept documents with an explicit “%YAML 1.2” directive, as well as documents lacking a “YAML” directive.

example yaml file:

%YAML 1.2

---
yapeal:
    application_agent: ""
    registered_mode: "optional"

Using:

$handler = new Yaml();
$result = $handler->parse($yapealYaml);
var_dump($result);
print PHP_EOL;

Expect:

Array
(
    [yapeal] => Array
        (
            [application_agent] =>
            [registered_mode] => optional
)

Get:

NULL

If I use %YAML 1.1 also get the same result. This is also covered in the above spec about how it should be handled.