Cannot Post Span Value By Document.form.submit

I'm writing a form and use document.form.submit() to post value, and I hope I can use x = http.formvalue('') to get the value well. But I found if I submit value then

Solution 1:

span is not a form element. Form elements are inputs, selects, radios, textareas, etc. That is why it works when you change it to an input.