Moodle check_user_existance

externallib.php

/**
 * Return description of check_user_existance paramters.
 * 
 * @return external_function_paramaters
 * @since Moodle 3.2
 */
public static function check_user_existence_parameters(){
    return new external_function_parameters(
        array(
            'username' => new external_value(core_user::get_property_type('username'), 'Username of the user'),
            'password' => new external_value(core_user::get_property_type('password'), 'User password'),
        )
    );
}
public static function check_user_existence($username, $password){
    global $CFG, $DB;

    $params = self::validate_parameters(self::check_user_existence_parameters(), 
        array('username' => $username, 'password' => $password));

    $validated_username = $params['username'];
    $validated_password = $params['password'];

    $valid = false;
    $messages = [];
    $data = [];

    // Check if data are provided.
    $datacheck = ['username' => !empty($validated_username), 'password' => !empty($validated_password)];

    if ($datacheck['username'] && $datacheck['password']){
        if ($user = $DB->get_record('user', array('username'=>$validated_username))) {
            $valid = validate_internal_user_password($user, $validated_password);
        }
    } else {
        $valid = false;
        if (!$datacheck['username']){
            $messages[] = [
                'key' => "username",
                'value' => "Username must be a valid name and not empty"
            ];
        }

        if (!$datacheck['password']){
            $messages[] = [
                'key' => "password",
                'value' => "Password must be a valid password and not empty"
            ];
        }
    }

    if (!$valid){
        $messages[] = [
            'key' => "error",
            'value' => "Username or Password are wrong, please try with correct data"
        ];
    }


    return array('valid' => $valid, 'data' => $data,'messages' => $messages);
}

/**
 * Returns description of check_user_existance
 *
 * @return external_description
 * @since Moodle 3.2
 */
public static function check_user_existence_returns() {

    return new external_single_structure(
            array(
                'valid' => new external_value(PARAM_BOOL, 'Are the provided credentials valid or not'),
                'data' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'key' => new external_value(PARAM_ALPHANUMEXT, 'The key of the data'),
                            'value' => new external_value(PARAM_RAW, 'The value of the data')
                        )
                    )
                ),
                'messages' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'key' => new external_value(PARAM_ALPHANUMEXT, 'The key of the message'),
                            'value' => new external_value(PARAM_TEXT, 'The content of the message')
                        )
                    )
                )
            )
    );
}