Moodle在表现层的实现有多种机制，分别针对页面、表单、导航条、页面头部、页面底部等。
1、针对页面的实现，直接编辑HTML页面，然后在业务逻辑处理完毕之后，include编辑好的html页面即可。这种机制的实现可以看login/index.php和 login/index_form.php页面。
2、针对表单的实现，一般是创建一个父类为moodleform的类，如
class test_form extends moodleform {
//定义表单元素
function definition() {
//获得表单引用
$mform =& $this->_form;
//添加header对象
$mform->addElement('header', '', get_string('createuserandpass'), '');
//添加text对象，
$mform->addElement('text', 'username', get_string('username'), 'maxlength="100" size="12"');
$mform->setType('username', PARAM_NOTAGS);
$mform->addRule('username', get_string('missingusername'), 'required', null, 'server');
}
//定义过滤
function definition_after_data(){}
//定义验证逻辑
function validation($data, $files) {}
}
然后，业务逻辑层中声明test_form对象，即
$test = new test _form();
最后调用test_form对象的display方法，即可把表单对象显示出来。
$test ->display();
表单元素的类型和规则如下：
$GLOBALS['HTML_QUICKFORM_ELEMENT_TYPES'] =
array(
'group' =>array('HTML/QuickForm/group.php','HTML_QuickForm_group'),
'hidden' =>array('HTML/QuickForm/hidden.php','HTML_QuickForm_hidden'),
'reset' =>array('HTML/QuickForm/reset.php','HTML_QuickForm_reset'),
'checkbox' =>array('HTML/QuickForm/checkbox.php','HTML_QuickForm_checkbox'),
'file' =>array('HTML/QuickForm/file.php','HTML_QuickForm_file'),
'image' =>array('HTML/QuickForm/image.php','HTML_QuickForm_image'),
'password' =>array('HTML/QuickForm/password.php','HTML_QuickForm_password'),
'radio' =>array('HTML/QuickForm/radio.php','HTML_QuickForm_radio'),
'button' =>array('HTML/QuickForm/button.php','HTML_QuickForm_button'),
'submit' =>array('HTML/QuickForm/submit.php','HTML_QuickForm_submit'),
'select' =>array('HTML/QuickForm/select.php','HTML_QuickForm_select'),
'hiddenselect' =>array('HTML/QuickForm/hiddenselect.php','HTML_QuickForm_hiddenselect'),
'text' =>array('HTML/QuickForm/text.php','HTML_QuickForm_text'),
'textarea' =>array('HTML/QuickForm/textarea.php','HTML_QuickForm_textarea'),
'link' =>array('HTML/QuickForm/link.php','HTML_QuickForm_link'),
'advcheckbox' =>array('HTML/QuickForm/advcheckbox.php','HTML_QuickForm_advcheckbox'),
'date' =>array('HTML/QuickForm/date.php','HTML_QuickForm_date'),
'static' =>array('HTML/QuickForm/static.php','HTML_QuickForm_static'),
'header' =>array('HTML/QuickForm/header.php', 'HTML_QuickForm_header'),
'html' =>array('HTML/QuickForm/html.php', 'HTML_QuickForm_html'),
'hierselect' =>array('HTML/QuickForm/hierselect.php', 'HTML_QuickForm_hierselect'),
'autocomplete' =>array('HTML/QuickForm/autocomplete.php', 'HTML_QuickForm_autocomplete'),
'xbutton' =>array('HTML/QuickForm/xbutton.php','HTML_QuickForm_xbutton')
);
$GLOBALS['_HTML_QuickForm_registered_rules'] = array(
'required' => array('html_quickform_rule_required', 'HTML/QuickForm/Rule/Required.php'),
'maxlength' => array('html_quickform_rule_range', 'HTML/QuickForm/Rule/Range.php'),
'minlength' => array('html_quickform_rule_range', 'HTML/QuickForm/Rule/Range.php'),
'rangelength' => array('html_quickform_rule_range', 'HTML/QuickForm/Rule/Range.php'),
'email' => array('html_quickform_rule_email', 'HTML/QuickForm/Rule/Email.php'),
'regex' => array('html_quickform_rule_regex', 'HTML/QuickForm/Rule/Regex.php'),
'lettersonly' => array('html_quickform_rule_regex', 'HTML/QuickForm/Rule/Regex.php'),
'alphanumeric' => array('html_quickform_rule_regex', 'HTML/QuickForm/Rule/Regex.php'),
'numeric' => array('html_quickform_rule_regex', 'HTML/QuickForm/Rule/Regex.php'),
'nopunctuation' => array('html_quickform_rule_regex', 'HTML/QuickForm/Rule/Regex.php'),
'nonzero' => array('html_quickform_rule_regex', 'HTML/QuickForm/Rule/Regex.php'),
'callback' => array('html_quickform_rule_callback', 'HTML/QuickForm/Rule/Callback.php'),
'compare' => array('html_quickform_rule_compare', 'HTML/QuickForm/Rule/Compare.php')
);
具体可以查看lib/pear/HTML/QuickForm.php，和各个表单元素和规则的实现文件。
来源：http://www.goodu.info/gc/node/354