Issue #3471412: Ignore phpstan function-not-found errors about functions that will exist at runtime

src/Plugin/PdfBackend/FillPdfServicePdfBackend.php

@@ -68,7 +68,9 @@ class FillPdfServicePdfBackend extends PdfBackendBase {
       $this->messenger()->addError($result['error']);
       $ret->error = TRUE;
     }
+    // @phpstan-ignore function.notFound (xmlrpc_error() is defined when xmlrpc() is executed)
     elseif ($result == FALSE || xmlrpc_error()) {
+      // @phpstan-ignore function.notFound
       $error = xmlrpc_error();
       $ret->error = TRUE;
       $this->messenger()->addError($this->t('There was a problem contacting the FillPDF service.