To elaborate on what was glossed already: PHP has no capacity greater than Perl's here. Perl probably has more support for JS as well and JSON::XS is the top of the heap (JSON is generally much more pleasant than XML with Ajax). To make your choice you should look at the available talent pool in your area / price-range probably and be warned there are plenty terrible programmers in both so check references and see that whomever you hire doesn't write disposable code; i.e., sites he/she has done live longer than a year or two without needing a rewrite.