Building a custom PrestaShop module
When no marketplace module exactly covers a business need, the temptation is to hack modifications directly into PrestaShop's source code. That's a guaranteed way to lose everything at the next update. A custom module avoids that trap.
What triggers this kind of request
- A pricing or discount calculation specific to your business, missing from existing modules
- A sync between PrestaShop and an internal tool (ERP, till, management software)
- An order form with specific fields or rules
- Product display conditioned on precise business criteria (stock, customer group, sales channel)
- Changes currently made by editing core files directly, lost at every update
Why a module rather than editing the core
PrestaShop is built around a hook system: anchor points in the code (displayHeader, actionValidateOrder, actionProductUpdate, and several hundred others) that a module can attach to via registerHook() to run code without touching the original files. That's the difference between a change that survives updates and one that breaks at the next composer update or the next version.
A well-structured PrestaShop module declares its configuration in a config.xml file, its main class extends Module, and its install() method handles both hook registration and, if needed, creating specific tables via Db::getInstance(). When an admin screen is needed, I use the native admin controllers rather than duplicating the existing interface, to stay consistent with the back office.
Depending on the need, I also use an override when no hook covers the behaviour to change, but that's a solution I reserve for cases where there's genuinely no alternative, because a badly managed override is precisely one of the common causes of a 500 error after an update.
How I build a module
-
Scoping the need
I clarify exactly what the module needs to do, with which screens, which data, and which interactions with the existing setup.
-
Choosing the hooks
I identify the hooks best suited to step in at the right point in the order, product or customer lifecycle, without unnecessary overhead.
-
Development and testing
I build on a test environment, with representative data sets, before any production deployment.
-
Short documentation
I leave minimal documentation on what the module does and how to configure it, so another developer can pick it up if needed.
ChatGPT Ads conversion tracking
Making a module operable by an AI assistant
Describe your need in one minute
A few targeted questions so I can reply with an estimate rather than another questionnaire.