Spry - pang visual presentation lang and i think wala sila'y ajax back-end support. but compared to other js libraries, mas smooth iya accordion, tabbed panels, and other widgets. so i use Spry for those things.
for ajax implementations i use a combination of Prototype and JQuery. I still use Prototype for basic ajax calls. I use JQuery for the (awesome!!!) plugins.
anyway, if you can use Java instead of PHP then mas maayo for an Accounting System and HRIS. Java for more intricate and accurate (money) calculations for your accounting system. Java for more accurate (employee related) date and time calculations for your HRIS.
Java also has very very good reporting tools: iReport, Jasper, Apache FOP. I've tried MPDF before, and I'm sorry to say but it sucks!!! it is very very limited in functionality and has very very scarce support.
although i'm not saying PHP sucks
it's just that it depends more on the type of application you want to build. PHP is excellent for social networking sites like (pero dili sa backend ha) Facebook, Friendster, etc... for business applications like the ones mentioned above, it's much better to use J2EE or .Net
for business applications I would recommend:
database : mysql
persistence layer : hibernate
server-side : java
framework : spring
client-side : adobe flex
or
client-side : jsp, ajax (spry, prototype, jquery, mootools if you can manage prototype compatibility), struts tiles
security : owasp stinger
search engine : solr
reporting : jasper
pdf rendering : apache fop
caching : ehcache or memcached for larger systems
server : tomcat, jboss, or glassfish (depends on the complexity of your application e.g. only use EJB if really needed but if not then don't use it) for most applications that are not too complex, tomcat will do