A wrapper to make a PHP object read only recursively.

ReadOnly.php

<?php

namespace Rekalogika\Util;

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;

/**
 * Make an object read only by recursively only allowing get*, is*, has*
 * methods, and specifically for Doctrine Collection: contains, containsKey,
 * get, getKeys, getValues, isEmpty, first, last, count.
 *
 * This assumes all the getter methods are really getters, and will not change
 * the object's attributes.
 *
 * If the method outputs an array, it will be converted into an ArrayCollection.
 *
 * The intended usage is to safely feed an object as an input for Symfony
 * Expression Language, and prevent it from being modified by the expression.
 *
 * @author Priyadi Iman Nurcahyo <priyadi@rekalogika.com>
 */
final class ReadOnly
{
    private $object;

    const COLLECTION_ALLOW = [
        'contains',
        'containsKey',
        'get',
        'getKeys',
        'getValues',
        'isEmpty',
        'first',
        'last',
        'count'
    ];

    public function __construct($object)
    {
        if (!is_object($object)) {
            throw new \InvalidArgumentException('Input is not an object');
        }

        $this->object = $object;
    }

    /**
     * __call magic method
     *
     * @param string $method
     * @param array $args
     * @return mixed
     */
    public function __call(string $method, array $args)
    {
        if ($this->object instanceof Collection) {
            if (!in_array($method, self::COLLECTION_ALLOW)) {
                throw new \BadMethodCallException('Method is blocked: ' . $method);
            }
        } else {
            if (!preg_match('/^(get|is|has)[A-Z]/', $method)) {
                throw new \BadMethodCallException('Method is blocked: ' . $method);
            }
            if (count($args) > 0) {
                throw new \BadMethodCallException('Using arguments is prohibited: ' . $method);
            }
        }

        $output = call_user_func_array([$this->object, $method], $args);

        if (is_object($output)) {
            return new self($output);
        } elseif (is_array($output)) {
            return new self(new ArrayCollection($output));
        } else {
            return $output;
        }
    }
}