i have this situation:
i was given an api written in xml. the purpose of the api is store data to an external server. and the data is coming from an html form encoded by the user. my Q is how am i going to transfer the data coming from <form> going to xml fields?

and what to do to send this xml file to the server? im really new to this..so guys i need ur advice

Well, XML is nothing more than a specially formatted text file, describing a structure of datas.

You can write it "manually", simply parsing the post fields, or you can use functions like xmlWriter to ease up the job.
See an exemple there:
http://www.php.net/manual/en/ref.xmlwriter.php#64484

As for saving the datas, you must ask the people who run the service you are submitting ths xml.
It could be via a web service (like SOAP, or REST), via a form submit, or opening and writing to a specific socket on their server.....

i wanted to have a <form> so that i can validate the entry of users. out of these data gathered from a form i will create an xml document. i already have the structure of the xml doc they want. in validating i will be using javascript and php.

-what is the best way to write this xml doc...via php or javascript?
-with reg to my first Q, the recipient of xml doc should be the one to inform me how am i going to submit the doc?

tnx a lot man..things got clear to me now