Php Moodle验证不起作用

我需要在提交时进行自定义验证，我的编码如下：

<?php

require_once("{$CFG->libdir}/formslib.php");

class pool_status_form extends moodleform {

   function definition() {
global $DB, $USER, $qnsCount;

       $mform =&$this->_form;
//number of question per user
$mform->addElement('text', 'peruser', get_string('peruserquestion', 'qpool'), array('id' => 'peerqn'));
$mform->addRule('peruser', null, 'required', null, 'client');
$mform->addRule('peruser', null, 'numeric', null, 'client');
$mform->setType('peruser', PARAM_RAW);


//$this->add_action_buttons(false, 'SAVE');
$mform->addElement('submit', 'subbtn', get_string("buttonlabel", "qpool"));

   }


public function validation($data, $files) {


$errors = parent::validation($data, $files);

if (($data['peruser'])>3) {

$errors['peruser'] = "Error..";

}

return $errors;
}
}

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“验证”功能在服务器上运行。只需调用$form->get_data（），它就会触发

另外，为什么要添加两次“必需”规则？ 为什么数据类型是PARAM_RAW？我觉得它像PARAM_INT