Ajax, PHP and MySQL. Why isn't db open?

[salewit]

After struggling with Ajax for a few years, I hunkered down and finally got into it. Not as difficult as it first seemed.

I do have one question regarding opening and closing the MySQL database.

Main Program

openMysqlDbFunction;
do some assorted stuff
Do the Ajax thing
do some db stuff
close database

PHP called by Ajax

do some db stuff

This will give me an error because the database is not opened.

PHP called by Ajax

openMysqlDbFunction;
do some db stuff

1) Why do I have to open it again even though it's open in the main calling program?
2) Because I'm opening it again in the Ajax PHP code, does that close the DB in the main program?
3) Suppose the Ajax routine is called several times in the Main Program. Am I not doing things cleanly? Should I close the DB in the Ajax/PHP code?

Thanks for the help.

[penders]

I initially wrote a reply regarding ajax/db but then wondered if you are referring to persistent database connections? (Although this is the JavaScript forum). Normal db connections are not persistent between requests. However, if you are querying the ajax/request process then persistent connections are probably best avoided and probably not required.

[rocknbil]

Why do I have to open it again even though it's open in the main calling program?

If I get you right, you mean "the page containing the ajax" when you say "main program." So this (PHP?) page opens a connection, outputs the data, closes connection. Your Ajax request, then, is like a separate "page" being called, it has to re-open a new connection to do "whatever." And when it's done, it closes again.