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Overriding default behaviors

PrestaShop enables you to override various default components and behaviors. This system consists of two major points:

  1. Overriding PrestaShop's own behavior (class files and controller files) in order to target a specific section of the required components.
  2. Overriding the visible parts of modules (Templates, JavaScript, style sheet language...) so that the themes can adapt better to them.

Overriding PrestaShop's classes and controllers

Overriding is a way to "override" class files and controller files. PrestaShop's ingenious class auto-loading function makes the "switch" to other files fairly simple. Thanks to PrestaShop's fully object-oriented code, you can rely on object inheritance to modify and add new behaviors, using the properties and methods of the various existing classes.

Classes and controllers are usually built following a certain norm. Here is the Product class and controller:

  • /classes/Product.php
    This class would be called ProductCore.
  • /controllers/front/ProductController.php
    This controller would be called ProductControllerCore.

You will need to create a PHP file and place it either of the override folders, depending on whether this file is part of a module, or distributed as-is. Indeed, since PrestaShop 1.5, there are two locations where you can place your overriding files: either at the root of the PrestaShop install, or within a module.

Overriding a class

In order to override the Product class, your file needs to be called Product.php and must feature a Product class that then extends ProductCore class.

The file can be placed in either of these locations:

  • /override/classes/Product.php
  • /modules/my_module/override/classes/Product.php

Overriding a controller

In order to override the ProductController class, your file needs to be called ProductController.php and must feature a ProductController class that then extends ProductControllerCore class.

The file can be placed in either of these locations:

  • /override/controllers/front/ProductController.php
  • /modules/my_module/override/controllers/front/ProductController.php

Overriding other behaviors

PrestaShop has certain files you can use to override elements such as displaying redirections (Tools.php) and measuring hook execution time (_Module.php), etc. you can enable them by removing the "_" prefix. For instance, rename _Tools.php into Tools.php. If there already exists a Tools.php override, you will have to merge it with yours.

Overriding a module's behavior

The modules are usually in the following format:

  • /modules/my_module/my_module.tpl
  • /modules/my_module/my_module.css
  • /modules/my_module/my_module.js
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Since PrestaShop 1.5, they can and should also be in the following format:

  • /modules/my_module/views/templates/front/my_module.tpl
  • /modules/my_module/views/templates/front/my_module.css
  • /modules/my_module/views/templates/front/my_module.js

PrestaShop allows you to override or replace certain front-office module files with new ones within the same theme. The override is governed by the theme: once it contains a /modules folder (or more!), PrestaShop will browse its content for files which have the same name and path as those of existing modules, and replace these with the new ones.

This means, for PrestaShop 1.4-compatible modules:

  • /themes/my_theme/modules/my_module/my_module.tpl
  • /themes/my_theme/css/modules/my_module/my_module.css
  • /themes/my_theme/js/modules/my_module/my_module.js

Since PrestaShop 1.5, the path is slightly longer

  • /themes/my_theme/modules/my_module/views/templates/front/my_module.tpl
  • /themes/my_theme/css/modules/my_module/views/templates/front/my_module.css
  • /themes/my_theme/js/modules/my_module/views/templates/front/my_module.js

In general, the proper path to override a .tpl, .js or .css file depends on the module's own path. That is the reason why if PrestaShop 1.5 has to work with a module without a view folder, it will need the same override path.
In short, you can keep overriding code in 1.5 just as you did in 1.4.

The new files will be used when the customer loads your shop.

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Contrary to the override code that is to be placed manually in the /override folder, module overrides are enabled as soon as the module is installed. During installation, overriding code is merge with those already in place (if any), otherwise they are copied to the /override folder at the root of the PrestaShop folder.

Manipulating the override code manually

Modules and themes may add an override to a default behavior, and PrestaShop takes care of reseting the /cache/class_index.php file.

But sometimes you need to add that overriding code yourself, manually uploading the file to your server. In that case, you need to trigger the regeneration of the /cache/class_index.php file yourself. This is done simply by deleting the file: if PrestaShop cannot find the file, it will regenerate it, taking all the overrides into account.

It is the same when manually removing an override: in order to reinstate the default behavior, you must delete the /cache/class_index.php file.

Sample code

Example 1

Using the MySQL.php data class is simply impossible while trying to enter data into a different database from PrestaShop's on the same MySQL Server. (Really!)

The solution is to use the following override of the MySQLCore class:

To use it you have to instantiate the class as follows:

  • For local connection: new MySQL(DB_SERVER, DB_USER, DB_PASSWD, 'DB_name', true);
  • For remote connection: new MySQL(DB_SERVER, DB_USER, DB_PASSWD, 'DB_name', true);

The last parameter forces the creation of a MySQL connection.

Example 2

Example 3

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