lib/formslib.php Validation

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There are two ways to add validation in the forms lib.

MoodleQuickForm::addRule()

You use this typically inside your moodleform::definition method. For example to set a field as required.



$mform->addElement('text','shortname', get_string('shortname'),'maxlength="15" size="10"');
$mform->setHelpButton('shortname', array('courseshortname', get_string('shortname')), true);
$mform->setDefault('shortname', get_string('defaultcourseshortname'));
$mform->addRule('shortname', null, 'required', null, 'client');
$mform->setType('shortname', PARAM_MULTILANG);

There is good documentation for this on the PEAR web site

In Moodle formslib you can set certain rules' error message to null and a default error message will automatically be used. The default messages are defined in lang/{language}/form.php. Here are the English definitions :

$string['err_alphanumeric']='You must enter only letters or numbers here.';
$string['err_email']='You must enter a valid email address here.';
$string['err_lettersonly']='You must enter only letters here.';
$string['err_maxlength']='You must enter not more than $a->format characters here.';
$string['err_minlength']='You must enter at least $a->format characters here.';
$string['err_nopunctuation']='You must enter no punctuation characters here.';
$string['err_nonzero']='You must enter a number not starting with a 0 here.';
$string['err_numeric']='You must enter a number here.';
$string['err_rangelength']='You must enter between {$a->format[0]} and {$a->format[1]} characters here.';
$string['err_required']='You must supply a value here.';

moodleform::validation()

Define a method validation on your moodleform child to make your own custom validation for the form. This is done on the server side. And data_submitted will return null until the function returns no errors. You return an array of errors if there is any error or an empty array if there are no errors.

class course_edit_form extends moodleform {
 
    function definition() {
        blah blah;
    }
 
    // Perform some extra moodle validation
    function validation($data, $files) {
        $errors= array();
        if ($foundcourses = get_records('course', 'shortname', $data['shortname'])) {
            if (!empty($data['id'])) {
                unset($foundcourses[$data['id']]);
            }
            if (!empty($foundcourses)) {
                foreach ($foundcourses as $foundcourse) {
                    $foundcoursenames[] = $foundcourse->fullname;
                }
                $foundcoursenamestring = implode(',', $foundcoursenames);
                $errors['shortname']= get_string('shortnametaken', '', $foundcoursenamestring);
            }
        }
 
        if (empty($data['enrolenddisabled'])){
            if ($data['enrolenddate'] <= $data['enrolstartdate']){
                $errors['enroldateendgrp'] = get_string('enrolenddaterror');
            }
        }
        return $errors;
    }
}
?>

Also, note that if you decide to override this method in your child class, depending of its hierarchy, you'll need to perform one call to its parent validation() method in order to avoid missing various checks. Although it may be not necessary if your form is direct descendant of moodleform (because it does not contain any check), it is safe, in all cases, to start the method with this call:

class gorgeous_form extends parent_form {
    ...
    ...
    // Perform some extra moodle validation
    function validation($data, $files) {
        $errors = parent::validation($data, $files);
        ...
        ...
    }
}

Moodle1.9 There is a new parameter $files in Moodle 1.9, it allows validation of uploaded files too.

function validation($data, $files) {
        $errors = parent::validation($data, $files);
        if (empty($files['userfile'])) {
            if (array_key_exists('url', $data)) {
                $errors['url'] = get_string('required');
            }
        }
        return $errors;
    }

Moodle1.9 To validate a recaptcha element use the following code inside the function validation($data) {

if (!empty($CFG->recaptchapublickey) && !empty($CFG->recaptchaprivatekey)) {
    $recaptcha_element = $this->_form->getElement('recaptcha_field_name');
    if (!empty($this->_form->_submitValues['recaptcha_challenge_field'])) {
        $challenge_field = $this->_form->_submitValues['recaptcha_challenge_field'];
        $response_field = $this->_form->_submitValues['recaptcha_response_field'];
        if (true !== ($result = $recaptcha_element->verify($challenge_field, $response_field))) {
            $errors['recaptcha_field_name'] = $result;
        }
    } else {
        $errors['recaptcha_field_name'] = get_string('missingrecaptchachallengefield');
    }
}

Validation and groups: an edge case

When validating elements which are added to your form via MoodleQuickForm::addGroup(), be sure to apply errors on the group and not individual elements.

If your form fields are defined as follows:

        $fields= array(
            $mform->createElement('text', 'field'),
            $mform->createElement('button', 'validatefield'),
        );
        $mform->addGroup($fields, 'group', '', '', false);

Your validation should do the following:

        if (!is_valid($data['field'])) {
            $errors['group'] = get_string('validationfailed', 'xxx_yyy');
        }