<?php

class PMoon{
	public $ast = array();
	
	public function __construct(){
		$this->ast = array('labelStatement' => create_function('$label', 'return array("type" => "LabelStatement", 
		                                                           "label" => $label);'
		                                                      )); 
	}
}

$moon = new PMoon;
$labelFunc = $moon->ast['labelStatement']('Foo bar');

var_dump($labelFunc);