I've used ajax a lot before, I just can remember details.
Here is what I need to do.
Use enters email & password on an html form.
form tag has "onSubmit = return chk_vals();"
In chk_vals I want to use ajax to run a php program on the server that looks up the entered email / password pair; if it finds a match it returns something I can use to disallow. If it DOES NOT find a match, OK.
I'd like a sample along these lines, I can "fill in the blanks". One thing I can't remember is how to the the php to "return" a value to the client.