Fix various compatibility issues with PHP 8

libs/swiftmailer/classes/Swift/Spool.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of SwiftMailer.
+ * (c) 2009 Fabien Potencier <fabien.potencier@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Interface for spools.
+ *
+ * @author Fabien Potencier
+ */
+interface Swift_Spool
+{
+    /**
+     * Starts this Spool mechanism.
+     */
+    public function start();
+
+    /**
+     * Stops this Spool mechanism.
+     */
+    public function stop();
+
+    /**
+     * Tests if this Spool mechanism has started.
+     *
+     * @return bool
+     */
+    public function isStarted();
+
+    /**
+     * Queues a message.
+     *
+     * @param Swift_Mime_Message $message The message to store
+     *
+     * @return bool Whether the operation has succeeded
+     */
+    public function queueMessage(Swift_Mime_Message $message);
+
+    /**
+     * Sends messages using the given transport instance.
+     *
+     * @param Swift_Transport $transport        A transport instance
+     * @param string[]        $failedRecipients An array of failures by-reference
+     *
+     * @return int The number of sent emails
+     */
+    public function flushQueue(Swift_Transport $transport, &$failedRecipients = null);
+}