Example how to use the TypeInterface to let extbase initialize objects from your database records

DateInterval.php

<?php
namespace AppZap\MyExt\Type;

use TYPO3\CMS\Core\Type\TypeInterface;

/**
 * In our application we have fields that store time intervals as minutes in the database.
 * In our code we want proper DateInterval objects, so we use a TypeInterface to let extbase take care of the conversion.
 * 
 * Usage example on a model property:
 * 
 *     /**
 *      * @var \AppZap\MyExt\Type\DateInterval
 *      * /
 *     protected $duration;
 * 
 */
class DateInterval extends \DateInterval implements TypeInterface
{

    /**
     * Constructs a DateInterval object from the minutes coming from the database
     * @param string $minutes
     */
    public function __construct($minutes)
    {
        parent::__construct('PT' . (int)$minutes . 'M');
    }

    /**
     * Returns the minutes for the DateInterval to store it in the database
     * @return string
     */
    public function __toString()
    {
        return (string)round($this->toSeconds() / 60);
    }

    /**
     * @return int seconds
     */
    protected function toSeconds()
    {
        $reference = new \DateTimeImmutable;
        $endTime = $reference->add($this);
        return $endTime->getTimestamp() - $reference->getTimestamp();
    }

}