PHP errors not displaying on OVH even though display_errors = on
This happens because OVH uses an optimised PHP infrastructure known as PHP-FPM. This system does not respect php.ini files
like PHP-CGI does.
Instead, there are settings in .ovhconfig which determine how PHP-FPM handles things like errors,
based on an environment setting. When environment = production, errors are not displayed.
There are a few solutions:
1. Change the .ovhconfig environment
Download the .ovhconfig file from your web hosting root.
Change the environment flag from production to development.
2. Disable PHP-FPM
You can modify the .ovhconfig to force the use of PHP-CGI instead.
This will allow you to use php.ini files. The new content for .ovhconfig will be:
app.engine=phpcgi
app.engine.version=5.4
N.b. that I have changed this advice from the documented version in which OVH said you should set the engine version to AUTO, but this will seemingly give you a very regressive PHP version of 4.4.9!!
3. Manually force errors to display
This is the least elegant solution. At the start of the PHP file you want to debug, add:
ini_set('display_errors', 1);
error_reporting(E_ALL);