[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: https://github.com/pkp/pkp-lib/issues/2996
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: https://github.com/pkp/ojs/blob/ojs-stable-3_1_1/plugins/paymethod/paypal/composer.json
they were not included in the OJS installation, so you need to install them.


Hi @Vitaliy,
how do I install this components?