code.php

<?php
    public function __call($name, $arguments)
    {
        $callTypeIndex = 3;
        if (substr($name, 0, 2) == "is") {
            $callTypeIndex = 2;
        }

        $callType = substr($name, 0, $callTypeIndex);
        $propertyName = substr($name, $callTypeIndex);

        switch (true) {
            case ($callType === 'get' && count($arguments) === 0):
                return $this->get($propertyName);

            case ($callType === 'add' && count($arguments) === 1):
                return $this->add($propertyName);

            case ($callType === 'set' && count($arguments) === 1):
                return $this->set($propertyName);

            case ($callType === 'is' && count($arguments) === 0):
                return $this->is($propertyName);

            default:
                return $this;
        }
    }