Fix various compatibility issues with PHP 8

libs/swiftmailer/classes/Swift/Transport/FailoverTransport.php

@@ -0,0 +1,88 @@
+<?php
+
+/*
+ * This file is part of SwiftMailer.
+ * (c) 2004-2009 Chris Corbyn
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Contains a list of redundant Transports so when one fails, the next is used.
+ *
+ * @author Chris Corbyn
+ */
+class Swift_Transport_FailoverTransport extends Swift_Transport_LoadBalancedTransport
+{
+    /**
+     * Registered transport currently used.
+     *
+     * @var Swift_Transport
+     */
+    private $_currentTransport;
+
+    // needed as __construct is called from elsewhere explicitly
+    public function __construct()
+    {
+        parent::__construct();
+    }
+
+    /**
+     * Send the given Message.
+     *
+     * Recipient/sender data will be retrieved from the Message API.
+     * The return value is the number of recipients who were accepted for delivery.
+     *
+     * @param Swift_Mime_Message $message
+     * @param string[]           $failedRecipients An array of failures by-reference
+     *
+     * @return int
+     */
+    public function send(Swift_Mime_Message $message, &$failedRecipients = null)
+    {
+        $maxTransports = count($this->_transports);
+        $sent = 0;
+        $this->_lastUsedTransport = null;
+
+        for ($i = 0; $i < $maxTransports
+            && $transport = $this->_getNextTransport(); ++$i) {
+            try {
+                if (!$transport->isStarted()) {
+                    $transport->start();
+                }
+
+                if ($sent = $transport->send($message, $failedRecipients)) {
+                    $this->_lastUsedTransport = $transport;
+
+                    return $sent;
+                }
+            } catch (Swift_TransportException $e) {
+                $this->_killCurrentTransport();
+            }
+        }
+
+        if (count($this->_transports) == 0) {
+            throw new Swift_TransportException(
+                'All Transports in FailoverTransport failed, or no Transports available'
+                );
+        }
+
+        return $sent;
+    }
+
+    protected function _getNextTransport()
+    {
+        if (!isset($this->_currentTransport)) {
+            $this->_currentTransport = parent::_getNextTransport();
+        }
+
+        return $this->_currentTransport;
+    }
+
+    protected function _killCurrentTransport()
+    {
+        $this->_currentTransport = null;
+        parent::_killCurrentTransport();
+    }
+}