I\'m currently working on a solution in php which queries an sql database. However, i want other website to be able to query the database (or the functions in php). I search
Sounds to me like you're inadvertently writing a web API. REST is hot these days, for good reason (they play well with javascript clients, for one).
Here is a thread that should give you lots to chew on.
you could build a rpc server (remote-procedure-call). It could be either xml-rpc or json-rpc.
Here are some good documentations
If Cross-Domain is your only concern, check out JSONP. You can also check the jsonp tag to learn more.
Try soap or rest.
If I understood right... if you want other sites to access your Database... Obviously...use jQuery :p to make the calls