<?php

class Environment {
    protected $_source;

    public final function __construct(array &$source = array()) {
            if (empty($source)) {$source = $_SERVER;}
        $this->_source = array();a
        foreach( $source as $key => $value ){
            $this->_source[ convertName($key) ] = &$source[$key];
        }
    }

    private function convertName( $key ){
        $functionName = implode('', array_map(function ($in) {return ucfirst($in);}, explode('_',       strtolower($key))));
        return $functionName;
    }

    protected function _get($key) {
        if (isset($this->_source[$key])) {return $this->_source[$key];} return NULL;
    }
}

$e = new Environment();

echo $e->HttpUserAgent;