AJAX API have come into being like for about anything from Mapping API of google, Charting and UI provided by JQuery, and better UI through Adobe Flex API using Action script, ExtJS library.
Server centric world have more sifted towards interoperability of Web services with WS-i ans JSR 21. For better utilisation of components written as web service can be consumed by any Java or .NET or COBOL or SAP or Oracle apps.
With web services defined by (WSDL) web services definition language And three components Service Broker, Service Requester, Service Provider interacting with Each other to Expose as web service not only comes interoperate but since all web service properties are in XML thus achieving portability to other platforms like Java web service can talk to .net web service passing property details in XML format.
Now if data fetched from databases in put into XML format. data Also become portable to and database ..like you can take data out from oracle in XML and import to SQL server and so on..
PHP not only was first to popularize AJAX but also first to introduce Restful web services.
now instead of SOAP request to server the client sends SOAP over http thus web service request is just like URL. This provided lot of flexibility and security. As Earlier firewalls were made to intercept http header request but not SOAP header request. There were things like Schema poisoning, SOAP injection etc.. But today’s firewalls can track these all to details we want.
With in few year code sifted more from server side to client side with AJAX, Json etc So from 90:10 ratio to present 60:40 the movement has be relentless. But it have been marred with all security concerns of code present at client side.
More and More code will move towards client with AJAX to Server code ration if 40:60 it will go to 50: 50 to may be 60:40.. As the number of chips available on client machine motherboard continue to increase with i7 being 1 master chip and 6 slave chips (its like tree of level 3. so 2^(3-1) = 7 CPU..
In future there might be 23 CPU in your system so we can execute more code in parallel
Read how this will effect programming: