Your PrestaShop hook renders nothing, and nothing is logged

A module hook that returns an empty string looks exactly like a module hook that was never called. PrestaShop gives you nothing to tell them apart: no error, no log entry, no stack trace, no fallback text. The page renders fine. Your block is just absent. We spent three releases of one module chasing this, and the cause turned out to be three different mechanisms stacked on top of each other. Each one alone is enough to make output vanish silently. This is what they are, in the order we peeled them off. The setup The module registers displayHeader and renders a small template: a <script> block that carries a public site key into the page, and a <style> block that hides a third-party badge. Roughly: public function hookDisplayHeader ( $params ) { $this -> context -> smarty -> assign ([ 'recaptcha_pubkey' => $this -> getActivePublicKey (), 'recaptcha_hide_badge' => $hideBadge , ]); return $this -> display ( __FILE__ , 'views/templates/front/header_script.tpl' ); } Deployed, cache cleared, hook registered, Design > Positions shows the module attached. Page source: nothing. Not the script, not the style, not even a stray whitespace. Mechanism 1: core swallows the exception Hook::callHookOn() wraps every module hook call in a try/catch. When debug mode is off, it catches whatever the hook throws and returns an empty string. No error, no log, no trace. That is a defensible design decision — one broken module should not take down a storefront — but as a debugging experience it is brutal. Every possible failure inside your hook, from a typo to a missing file to a template that will not compile, arrives at your screen as the exact same symptom: nothing. The first thing to do, before theorising about causes, is to stop letting core swallow it: try { return $this -> display ( __FILE__ , 'views/templates/front/header_script.tpl' ); } catch ( Throwable $e ) { $message = 'mymodule header_script.tpl render failed: ' . $e -> getMessage () . ' in ' . $e -> getFile () . ':' . $e -> g