Grab a copy of a existing project written in Perl that comes as close as possible to the customers requirements. Preferably one that makes heavy use of as many CPAN modules as possible. Skin it to have your customers name and colours. Ie. Spend 1 day doing a shallow mock-up.

Then ask the customer to view this "quick mock-up written in Perl" to get his thoughts on layout, colors etc. Explain that you are just leveraging an old project to get something to talk about quickly.

Then explain that the first thing you are going to do is have to re-write modules X,Y,Z & P,Q,R & A, B, C in PHP so that you can avoid having to write all the back-end code from scratch. Try and get him to visit CPAN himself.

Fill an email with direct links to the modules that you would normally use for such a project in Perl, and ask him if he knows of any equivalent free modules in PHP, so that you can avoid re-inventing the wheel (at his expense).

If he says "Yes", he's saved you some time, but he might stop to think about his pocket book rather than buzz phrases.