Aktualna data plus liczba dni

<?php

class ConvertIntToDateByDayNumbers {
    
    /**
     * if parameter is integer and is greater than zero adds to actual date number days == $expire otherwise function return default value
     * 
     * @param string $expire
     * @return string
     */
    public static function init(string $expire):string {

        if (!is_numeric($expire) || $expire < 0) {
            return $expire;
        }

        return date('Y-m-d', strtotime("+" . $expire . "days"));
    }

}