<?php

class Form {
	public $data = [];
	public $fields;
	
	function __construct($fields) {
		$this->fields = $fields;
		foreach($this->fields as &$field) {
			$this->data[$field['id']] = &$field['value'];
		}
	}
}

$f = new Form([
	[
		'id' => 'fname',
		'value' => 'George'
	],
	[
		'id' => 'lname',
		'value' => 'Lucas'
	]
]);

echo $f->data['fname'], $f->fields[0]['value'];
$f->data['fname'] = 'Ralph';
echo $f->data['fname'], $f->fields[0]['value'];