Just offering a simple solution. Obviously it's best to fix the problem BUT if he's got a simple site and incorporates an older script and the only errors he gets is a bunch of undefined variables technically there's no harm with turning those errors off.
It's important to understand how PHP's built in error reporting works anyways - I'd never let a client site go live fully opened up as naturally there may be a bump or 2 in the road. Build a custom error_log scheme and that will let you know whats wrong and not make your client look like an amature.