typeChecking.php

<?php

class TypeCheckingObject {
    /** @var string */
    private $storage = '';

    /**
     * @return string
     */
    public function getStorage() : string
    {
        return $this->storage;
    }

    /**
     * @param string $data
     */
    public function setStorage(string $data)
    {
        $this->storage = $data;
    }
}

$obj = new TypeCheckingObject();

$obj->setStorage(intval(10));

var_dump($obj->getStorage());