I created a profile where,after registration and login in
Someone can view his dteails.
How can I do so that,he/she will be able to edit/update that same profile,
after login in.
i use "User" and password in login in.
Help please!!!

do you use a database or file?
when having a db:

"UPDATE `profile` SET `hobbies`='coolstuff'  WHERE `user`=".$user

with a file you can do it the same way as createing it:

$f=fopen("...","w");
fwrite("hobbies:coolstuff\n");
fclose($f);

if you still have probs then post that little piece of code.

thank you, i use Database and after trying as u illustrated it worked.