Can an employer lay off an employee without paying accrued vacation time in PA?

The issue of whether you are paid accrued paid time off is a function of company policy. If their standard procedure is to pay employees for accrued time off, you get paid, if not, you don't. For instance, some companies have a 'use it or lose it' policy regarding PTO and if you don't use it in the year or within a short time after it accrues, you lose it.

If their policy is to pay it, and you aren't paid it within two weeks of your departure from employment, it is a violation of the Wage Payment Collection Law which entitles you to liquidated damages in addition to the unpaid PTO plus counsel fees.

Consider, however, that the amount in issue may not make it worthwhile for you to hire counsel. That is entirely up to you.