Doctrine Expression API

gistfile1.php

<?php
interface Updatable
{
    public function apply(Expression $e);
}

// Solution 1
// More powerful, but needs to parse and evaluate the string
class Expression
{
    public $criteria;
    public function set($field, $value);
}

$expression->set('position', 'position + 1');

// Solution 2
// Easier to implement, more limited
class Expression
{
    public $criteria;
    public function setValue($field, $value);
    public function setValueFromField($targetField, $sourceField);
    public function add($field, $number);
    public function multiply($field, $number);
    public function divide($field, $number);
}