Here is the issue :
Fatal error: Declaration of League\Container\ImmutableContainerAwareTrait::getContainer() must be compatible with League\Container\Argument\ArgumentResolverTrait::getContainer(): Psr\Container\ContainerInterface in /home/placeser/www/cdf/wp-content/plugins/wp-rocket/vendor/league/container/src/Inflector/Inflector.php on line 9
Fatal error: Declaration of League\Container\ImmutableContainerAwareTrait::getContainer() must be compatible with League\Container\Argument\ArgumentResolverTrait::getContainer(): Psr\Container\ContainerInterface in /home/placeser/www/cdf/wp-content/plugins/wp-rocket/vendor/league/container/src/Inflector/Inflector.php on line 9