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🚨 Emergency · Response within 30 min during business hours

500 error on your PrestaShop?
we fix it today.

Diagnostic and resolution of PrestaShop 500 errors by a certified expert

HTTP ERROR 500, Internal Server Error, blank page with a 500 header: your store is visible but unusable. We read the logs, identify the root cause, bring the site back online within 2 hours in 9 out of 10 cases.

Or call directly: +33 6 78 85 05 63
✓ Free diagnostic ✓ Firm quote within 24 business hours ✓ From €60/h excl. VAT ✓ No commitment
👀 What do you see?

The 9 faces of a PrestaShop 500 error

Describe what you see. The more precise, the faster the diagnostic.

🔴 Chrome / Firefox page HTTP ERROR 500
This page isn't working → Fatal server error
🔴 Apache 500 Internal Server Error
The server encountered an
internal error... → Default Apache page
🔴 Nginx 500 Internal Server Error
nginx/1.x.x → PHP-FPM down or crashed
🔴 PrestaShop debug ON Fatal error: Allowed memory
size of 134217728 bytes
exhausted → Memory limit exceeded
🔴 PHP autoloader PHP Fatal error: Uncaught
Error: Class "XYZ" not
found in /classes/... → Broken override / missing class
🔴 Fatal hook PHP Fatal error: Uncaught
Exception in /modules/
mymodule/hook.php:42 → Faulty module
🔴 mod_fcgid mod_fcgid: HTTP_INTERNAL_
SERVER_ERROR error,
premature end of script → PHP-CGI timeout
🔴 Corrupted .htaccess Invalid command 'RewriteEngine',
perhaps misspelled or
defined by a module not
included... → Regenerate .htaccess
🔴 Symfony (PS 8.x / 9.x) RuntimeException:
The service "..." has a
dependency on a non-existent
service "..." → Broken Symfony container
🔎 Technical causes

The 7 most frequent causes of a PrestaShop 500

Identified across 80+ emergency interventions. One may be present, or several stacked.

1. PHP memory_limit exhaustion

Most common (~35% of cases). Caused by a hook on actionProductSave loading all combinations into memory, a looping Doctrine migration, or an oversized catalogue export. Visible in error_log as Allowed memory size of X bytes exhausted. Fix: raise memory_limit to 512M or 1024M in php-fpm pool or php.ini, but most importantly identify the guilty hook.

2. Corrupted or wrongly regenerated .htaccess

~20% of cases. Happens after BO regeneration (Preferences → SEO & URLs), domain migration, or a PrestaShop update overwriting custom directives (compression, redirects). Typical Apache error: Invalid command 'RewriteEngine'. Fix: compare with previous git version, restore custom rules, ensure mod_rewrite is enabled.

3. Broken class override

~15%. After a PrestaShop update, overrides in /override/classes/ and /override/controllers/ may reference methods that changed signature or disappeared. PHP throws Fatal error: Class "X" not found or Cannot redeclare method Y. Fix: temporarily disable /override/ by renaming it, identify the faulty file, port it to the new version.

4. Faulty module after PrestaShop update

~12%. A module built for PrestaShop 1.7 never audited against PHP 8.x, or an external module that didn't follow a 1.7 → 8.x bump. PHP rejects strict typing (TypeError) or deprecated syntax. Fix: disable the module via SQL (UPDATE ps_module SET active=0 WHERE name='X') or remove its folder, find the vendor fix, deploy a local patch if needed.

5. Incorrect file permissions

~8%. Typically occurs after a brutal FTP restore or a host migration (Kinsta, WP Engine, SiteGround). PHP-FPM can no longer read /var/cache/prod/, write to /var/logs/, or execute a CLI script. Apache log: Permission denied. Fix: chmod -R 755 dirs / 644 files, chown -R www-data:www-data on sensitive folders.

6. Invalid Symfony container (PS 8.x / 9.x)

~6%. Specific to modern versions. A module declares a service with a dependency that doesn't exist, or a wrongly named services.yml. PrestaShop returns 500 at bootstrap, before even touching Smarty. Fix: clear /var/cache/prod/, run php bin/console cache:clear, inspect the suspect module's services.yml, declare the missing service or remove the phantom dependency.

7. Divergent PHP / OPCache configuration

~4%. OPCache still serving stale code after a deploy, display_errors=Off hiding the real cause, max_execution_time too low killing long scripts (CSV import, sitemap generation). Fix: restart PHP-FPM, audit phpinfo(), align php.ini CLI vs FPM.

💰 Pricing

Pricing stated up-front

Free diagnostic. For the intervention, you know exactly what it costs before we touch the code.

🔍 Diagnostic

Diagnostic

understand the 500
0€free
30 min · no commitment
  • Reading error_log + php-fpm.log
  • Root cause identified (memory_limit, .htaccess, override...)
  • Firm quote sent immediately
  • You decide if we continue
Start the diagnostic →
⚡ Most requested 🔧 Intervention

Targeted intervention

bring the site back online
from 60€excl. VAT
per diagnostic · price stated up-front
  • Backup of files + DB before any intervention
  • Targeted fix for the 500 (hook, .htaccess, override, module)
  • Tests front + back-office + checkout flow
  • Written report: root cause + fix applied
  • 30-day warranty on the fix
🛡️ Maintenance

Monthly maintenance

never relive a 500 again
from 50€/ month
24/7 monitoring · no commitment
  • 5-min uptime monitoring · SMS alert before your customers
  • Daily backups externalised to S3 / Backblaze
  • Priority intervention on 500 incidents
  • PrestaShop CVE watch + hotfix applied
❓ FAQ

PrestaShop 500 errors — frequently asked questions

A 500 error means Apache or Nginx tried to execute your PrestaShop code but encountered a fatal error it cannot return to the browser. Most common causes: PHP memory_limit exhaustion (often a module hook on product pages), corrupted .htaccess after regeneration or migration, broken class override after a PrestaShop update, wrong file permissions, or a module throwing an uncaught exception during bootstrap. Diagnostic always requires reading error_log and php-fpm.log, never a guess.
No. Every intervention starts with an externalised files + database backup. Fixes are first tested on staging when possible. Orders, customers, catalogue, media are never touched without validation. In 99% of cases, a PrestaShop 500 is a configuration or code issue, not a data issue.
Free initial diagnostic (30 min). Intervention then on quote, hourly rate from €60/h excl. VAT depending on complexity. Most 500 errors are resolved in 1 to 3 hours once the root cause is identified. Firm quote sent within 24 business hours, before any work starts: you know what you pay before we touch the site. Sites under Business or Performance maintenance get this intervention included.
For a standard 500 (memory_limit, .htaccess, fatal hook), the site is back online within 2 hours of intervention start, including 15-30 min of diagnostic. For complex cases (corrupted override, module conflict after major update), expect half a day to a full day. ETA stated after the free initial diagnostic, never afterwards.
No. To fix a 500, we need to read Apache / Nginx / PHP logs and often modify .htaccess, config/defines.inc.php, or an override. This requires FTP or SSH access. If you've lost your credentials, we first recover them from your host (Kinsta, WP Engine, SiteGround, GoDaddy, OVH). Typically 1 to 4 hours depending on the provider.
All of them: PrestaShop 1.6, 1.7, 8.x and 9.x can generate a 500. On 1.6 / 1.7, recurring culprits are old modules never audited against PHP 8.x. On 8.x / 9.x, more often Symfony container errors or services injected by modules. KLN-WEB is certified PrestaShop Expert CORE SKILLS across all versions.

500 on your site right now?

Describe what you see. We look within 30 min during business hours. Free diagnostic, firm quote within 24 business hours.

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