Example module for prestashop 1.6 with config page

lf_settings.php

<?php
if (!defined('_PS_VERSION_')) {
    exit;
}

class Lf_settings extends Module
{
    private $settings = [
        'lf_settings_support_email' => '[email protected]',
        'lf_settings_support_phone_1' => '+33 333 33333333',
        'lf_settings_support_phone_2' => '+32 333 33333333',
        'lf_settings_support_phone_3' => '+34 333 33333333',
    ];

    public function __construct()
    {
        $this->name = 'lf_settings'; // MUST be the same as module folder name
        $this->tab = 'front_office_features';
        $this->version = '1.0.0';
        $this->author = 'Author Name';
        $this->need_instance = 0;
        $this->ps_versions_compliancy = array('min' => '1.6', 'max' => _PS_VERSION_);
        $this->bootstrap = true;

        parent::__construct();

        $this->displayName = $this->l('LF Settings');
        $this->description = $this->l('Settings module');

        $this->confirmUninstall = $this->l('Are you sure you want to uninstall?');

        if (!Configuration::get('lf_settings'))
            $this->warning = $this->l('No name provided');


    }

    /**
     * Despite it's name this function actually saves the data from the POST request to the database
     * @return string
     */
    public function getContent()
    {
        $output = null;

        if (Tools::isSubmit('submit' . $this->name)) {
            $lf_settings_support_email = strval(Tools::getValue('lf_settings_support_email'));
            if (!$lf_settings_support_email
                || empty($lf_settings_support_email)
                || !Validate::isGenericName($lf_settings_support_email)
            )
                $output .= $this->displayError($this->l('Invalid Configuration value'));
            else {
                Configuration::updateValue('lf_settings', $lf_settings_support_email);
                $output .= $this->displayConfirmation($this->l('Settings updated'));
            }
        }
        return $output . $this->displayForm();
    }

    public function displayForm()
    {
        // Get default language
        $default_lang = (int)Configuration::get('PS_LANG_DEFAULT');

        // Init Fields form array
        $fields_form[0]['form'] = array(
            'legend' => array(
                'title' => $this->l('Settings'),
            ),
            'input' => $this->getInputsForDisplayForm(),
            'submit' => array(
                'title' => $this->l('Save'),
                'class' => 'btn btn-default pull-right'
            )
        );

        $helper = new HelperForm();

        // Module, token and currentIndex
        $helper->module = $this;
        $helper->name_controller = $this->name;
        $helper->token = Tools::getAdminTokenLite('AdminModules');
        $helper->currentIndex = AdminController::$currentIndex . '&configure=' . $this->name;

        // Language
        $helper->default_form_language = $default_lang;
        $helper->allow_employee_form_lang = $default_lang;

        // Title and toolbar
        $helper->title = $this->displayName;
        $helper->show_toolbar = true;        // false -> remove toolbar
        $helper->toolbar_scroll = true;      // yes - > Toolbar is always visible on the top of the screen.
        $helper->submit_action = 'submit' . $this->name;
        $helper->toolbar_btn = array(
            'save' =>
                array(
                    'desc' => $this->l('Save'),
                    'href' => AdminController::$currentIndex . '&configure=' . $this->name . '&save' . $this->name .
                        '&token=' . Tools::getAdminTokenLite('AdminModules'),
                ),
            'back' => array(
                'href' => AdminController::$currentIndex . '&token=' . Tools::getAdminTokenLite('AdminModules'),
                'desc' => $this->l('Back to list')
            )
        );

        // Load current value
        $this->addFieldsValuesToHelper($helper);

        return $helper->generateForm($fields_form);
    }

    /**
     * @param $helper
     */
    private function addFieldsValuesToHelper($helper)
    {
        foreach ($this->settings as $name => $value) {
            $helper->fields_value[$name] = Configuration::get($name);
        }
    }

    public function getConfigFieldsValues()
    {
        $fields = [];

        foreach ($this->settings as $name => $value) {
            $fields[$name] = Tools::getValue($name, Configuration::get($name));
        }

        return $fields;
    }

    public function reset()
    {
        if (!$this->uninstall())
            return false;
        if (!$this->install())
            return false;

        return true;
    }

    public function uninstall()
    {
        if (!parent::uninstall()) {
            return false;
        }

        return $this->removeSettingsFromDB();
    }

    private function removeSettingsFromDB()
    {
        foreach ($this->settings as $name => $value) {
            if (!Configuration::deleteByName($name)) {
                return false;
            }
        }
        return true;
    }

    public function install()
    {
        if (!parent::install()) {

            return false;
        }
        $this->createSettingsInDB();

        return true;
    }

    private function createSettingsInDB()
    {
        foreach ($this->settings as $name => $value) {
            Configuration::updateValue($name, $value);
        }
    }

    private function getInputsForDisplayForm()
    {
        return [
            [
                'type' => 'text',
                'label' => $this->l('Support Email'),
                'name' => 'lf_settings_support_email',
                'size' => 100,
                'required' => true
            ],
            [
                'type' => 'text',
                'label' => $this->l('Support Phone 1'),
                'name' => 'lf_settings_support_phone_1',
                'size' => 100,
                'required' => true
            ],
            [
                'type' => 'text',
                'label' => $this->l('Support Phone 2'),
                'name' => 'lf_settings_support_phone_2',
                'size' => 100,
                'required' => true
            ],
            [
                'type' => 'text',
                'label' => $this->l('Support Phone 3'),
                'name' => 'lf_settings_support_phone_3',
                'size' => 100,
                'required' => true
            ],
        ];
    }
}