函数原型
function drupal_build_form($form_id, &$form_state) { //--- }
1 填充$form_state
$form_state += form_state_defaults();
2 填充$form_state[‘input‘]
if (!isset($form_state[‘input‘])) {
$form_state[‘input‘] = $form_state[‘method‘] == ‘get‘ ? $_GET : $_POST;
}
3 retrieve form 从函数中取出$form数组
$form = drupal_retrieve_form($form_id, $form_state);
4 prepare form
drupal_prepare_form($form_id, $form, $form_state);
5 process form
drupal_process_form($form_id, $form, $form_state);
6 返回$form变量, 供render函数渲染
return $form;
==== prepare form 和 process form 函数的形参是一样的
原文：http://www.cnblogs.com/qinqiu/p/4494093.html