# Using the backward compatibility toolkit

## Description <a href="#usingthebackwardcompatibilitytoolkit-description" id="usingthebackwardcompatibilitytoolkit-description"></a>

PrestaShop's module API has greatly improved since version 1.4 of the software, and the API in version 1.5 and 1.6 is quite different.

Because there is a huge ecosystem of modules that are being upgraded to support the 1.5/1.6 module API while many shops are still using PrestaShop 1.4, the developers of PrestaShop chose to build Backward Compatibility, a free toolkit which is only available for PrestaShop 1.4, and makes it possible to make 1.5/1.6 modules work in PrestaShop 1.4.

Including this toolkit makes it possible to develop a 1.4 module that uses PrestaShop 1.5/1.6 standards.

The 1.5/1.6 API's Helpers (HelperForm, HelperView, etc.) are still not available in PrestaShop 1.4.

Therefore, the following declarations are not necessary anymore:

```
global $smarty, $cookie;
```

The information they provide is available through these calls:

```
$this->context->customer->id;
$this->context->language->id;
$this->context->smarty->assign('content', 'empty');
...
```

## Download and install <a href="#usingthebackwardcompatibilitytoolkit-downloadandinstall" id="usingthebackwardcompatibilitytoolkit-downloadandinstall"></a>

You can download it directly from PrestaShop's repository: <https://github.com/PrestaShop/PrestaShop-backward_compatibility> .\
Just clone the Git project, then copy the `/backward_compatibility` folder to the root folder of the module you are developing. For instance, if your module is called TestModule, the folder should be here: `/modules/testmodule/backward_compatibility`.

The `/backward_compatibility` folder should contain the following files:

* `backward.ini`: the version number of the toolkit.
* `backward.php`: the main code.
* `Context.php`: adds a Context-like support to PrestaShop 1.4, as well as backward compatible Controller- and Customer-like methods.
* `Display.php`: enables the display of TPL files in the back office.
* `index.php`: just a file to prevent the display of the folder to visitors.

It is useless to install the toolkit in PrestaShop 1.5 or PrestaShop 1.6.

## How to use the module <a href="#usingthebackwardcompatibilitytoolkit-howtousethemodule" id="usingthebackwardcompatibilitytoolkit-howtousethemodule"></a>

To properly us the module, you must first declare it in the module constructor method:

```
public function __construct()
{
    $this->name = 'testmodule';
    $this->tab = 'other';
    $this->version = '0.1';
    $this->author = 'Firstname Lastname';
    $this->need_instance = 0;

    parent::__construct();

    $this->displayName = $this->l('Test module');
    $this->description = $this->l('This is a test module');
    $this->confirmUninstall = $this->l('Warning: all the data saved in your database will be deleted. Are you sure you want uninstall this module?');

    /* Backward compatibility */
    if (_PS_VERSION_ < '1.5')
           require(_PS_MODULE_DIR_.$this->name.'/backward_compatibility/backward.php');
}
```

Once this is in place, you can use more of the 1.5/1.6 API's goodness, such as the Context.


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