[OJS] Paypal black page

Hi everybody,
in my OJS installation when I click on the link in the paypal payment request email to publish an article, it shows me a blank page with this error:

Fatal error: Interface ‘Symfony\Component\EventDispatcher\EventSubscriberInterface’ not found in /var/www/vhosts/pagepress.org/httpdocs/medicine/plugins/paymethod/paypal/vendor/guzzle/guzzle/src/Guzzle/Http/RedirectPlugin.php on line 20

is it possible to correct it?
Thanks for the support.


Hi @Tiziano

Take a look at this discussion: Paypal plugin has undeclared dependency · Issue #2996 · pkp/pkp-lib · GitHub
You will need to install dependency:

cd plugins/paymethod/paypal
composer install

Hi @Vitaliy,
I’ve followed the instructions but you’re giving me this message:

-bash: composer: command not found

Composer roughly is an installator for PHP packages. The message means that it’s not installed on the system. You can either install it on the server and than run that command, or manually install the needed package.

Hi @Vitaliy,
why did you know this composer to run the paypal payment?

composer.json tells you what additional packages the plugin requires: ojs/composer.json at ojs-stable-3_1_1 · pkp/ojs · GitHub
they were not included in the OJS installation, so you need to install them.

We went through this problem with an earlier version 3. It recurred again when upgrading to so why was’nt applying the patch included in the upgrade?

Hi @nickpanes,

There was an exclusion of a necessary library from the .tar.gz build process. I’ve fixed it here, and it’ll be included in the next release. Meanwhile (up to and including OJS 3.1.2) you’ll need to update the composer dependencies yourself.

Alec Smecher
Public Knowledge Project Team

Thanks, good to know.