Just to be sure, do you want to translate from the "Georgian" calendar, which is an old calendar only used in the country/area of Georgia, or from the "Gregorian" calendar, which is the calendar currently in use throughout most of the world now?
In either case, I don't think there's any built-in functionality in PHP to handle it, so I'd try a google search on something like "php convert georgian to jalali" or "php convert gregorian to jalali" to see if there are existing libraries or functions you could use.