diff --git a/src/Model/Contact.php b/src/Model/Contact.php
index 5d1e92f4bc..a6bb882e86 100644
--- a/src/Model/Contact.php
+++ b/src/Model/Contact.php
@@ -359,7 +359,7 @@ class Contact
 	 * @throws HTTPException\InternalServerErrorException
 	 * @throws \ImagickException
 	 */
-	public static function isFollowerByURL(string $url, uid $uid): bool
+	public static function isFollowerByURL(string $url, int $uid): bool
 	{
 		$cid = self::getIdForURL($url, $uid);
 
@@ -1169,11 +1169,11 @@ class Contact
 	 * @throws HTTPException\InternalServerErrorException
 	 * @throws \ImagickException
 	 */
-	public static function getIdForURL(string $url, int $uid = 0, $update = null, array $default = []): int
+	public static function getIdForURL(string $url = null, int $uid = 0, $update = null, array $default = []): int
 	{
 		$contact_id = 0;
 
-		if ($url == '') {
+		if (empty($url)) {
 			Logger::notice('Empty url, quitting', ['url' => $url, 'user' => $uid, 'default' => $default]);
 			return 0;
 		}
diff --git a/src/Protocol/ActivityPub/Processor.php b/src/Protocol/ActivityPub/Processor.php
index cc869e00ee..c6420436e8 100644
--- a/src/Protocol/ActivityPub/Processor.php
+++ b/src/Protocol/ActivityPub/Processor.php
@@ -900,7 +900,7 @@ class Processor
 		}
 
 		// Store send a follow request for every reshare - but only when the item had been stored
-		if ($stored && ($item['private'] != Item::PRIVATE) && ($item['gravity'] == GRAVITY_PARENT) && ($item['author-link'] != $item['owner-link'])) {
+		if ($stored && ($item['private'] != Item::PRIVATE) && ($item['gravity'] == GRAVITY_PARENT) && !empty($item['author-link']) && ($item['author-link'] != $item['owner-link'])) {
 			$author = APContact::getByURL($item['owner-link'], false);
 			// We send automatic follow requests for reshared messages. (We don't need though for forum posts)
 			if ($author['type'] != 'Group') {
diff --git a/src/Protocol/DFRN.php b/src/Protocol/DFRN.php
index edd6c1450e..625afb215a 100644
--- a/src/Protocol/DFRN.php
+++ b/src/Protocol/DFRN.php
@@ -48,10 +48,10 @@ use Friendica\Network\Probe;
 use Friendica\Util\Crypto;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Images;
-use Friendica\Util\Network;
 use Friendica\Util\Proxy;
 use Friendica\Util\Strings;
 use Friendica\Util\XML;
+use GuzzleHttp\Psr7\Uri;
 
 /**
  * This class contain functions to create and send DFRN XML files
@@ -1013,7 +1013,7 @@ class DFRN
 			$path_parts = explode('/', $parts['path']);
 			array_pop($path_parts);
 			$parts['path'] =  implode('/', $path_parts);
-			$contact['batch'] = Network::unparseURL($parts);
+			$contact['batch'] = Uri::fromParts($parts);
 		}
 
 		$dest_url = ($public_batch ? $contact['batch'] : $contact['notify']);
diff --git a/src/Protocol/Diaspora.php b/src/Protocol/Diaspora.php
index 838d405505..6d3c23dad6 100644
--- a/src/Protocol/Diaspora.php
+++ b/src/Protocol/Diaspora.php
@@ -50,6 +50,7 @@ use Friendica\Util\Network;
 use Friendica\Util\Strings;
 use Friendica\Util\XML;
 use Friendica\Worker\Delivery;
+use GuzzleHttp\Psr7\Uri;
 use SimpleXMLElement;
 
 /**
@@ -755,14 +756,14 @@ class Diaspora
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 * @throws \ImagickException
 	 */
-	private static function key(string $handle): string
+	private static function key(string $handle = null): string
 	{
 		$handle = strval($handle);
 
 		Logger::notice("Fetching diaspora key for: " . $handle);
 
 		$fcontact = FContact::getByURL($handle);
-		if ($fcontact) {
+		if (!empty($fcontact['pubkey'])) {
 			return $fcontact['pubkey'];
 		}
 
@@ -1417,7 +1418,7 @@ class Diaspora
 
 			$parts = parse_url($person['url']);
 			unset($parts['path']);
-			$host_url = Network::unparseURL($parts);
+			$host_url = Uri::fromParts($parts);
 
 			return $host_url . '/objects/' . $guid;
 		}
@@ -4006,12 +4007,12 @@ class Diaspora
 	/**
 	 * Sends profile data
 	 *
-	 * @param int  $uid    The user id
-	 * @param bool $recips optional, default false
+	 * @param int   $uid    The user id
+	 * @param array $recips optional, default empty array
 	 * @return void
 	 * @throws \Exception
 	 */
-	public static function sendProfile(int $uid, bool $recips = false)
+	public static function sendProfile(int $uid, array $recips = [])
 	{
 		if (!$uid) {
 			return;
diff --git a/src/Protocol/Email.php b/src/Protocol/Email.php
index 7584518449..79ad16ed2f 100644
--- a/src/Protocol/Email.php
+++ b/src/Protocol/Email.php
@@ -115,13 +115,13 @@ class Email
 	}
 
 	/**
-	 * @param Connection|resource $mbox mailbox
-	 * @param integer             $uid  user id
+	 * @param Connection|resource $mbox     mailbox
+	 * @param string              $sequence
 	 * @return mixed
 	 */
-	public static function messageMeta($mbox, int $uid)
+	public static function messageMeta($mbox, string $sequence)
 	{
-		$ret = (($mbox && $uid) ? @imap_fetch_overview($mbox, $uid, FT_UID) : [[]]); // POSSIBLE CLEANUP --> array(array()) is probably redundant now
+		$ret = (($mbox && $sequence) ? @imap_fetch_overview($mbox, $sequence, FT_UID) : [[]]); // POSSIBLE CLEANUP --> array(array()) is probably redundant now
 		return (count($ret)) ? $ret : [];
 	}
 
@@ -296,6 +296,7 @@ class Email
 			}
 			return $x;
 		}
+		return '';
 	}
 
 	/**
@@ -571,7 +572,7 @@ class Email
 	 * @param string $message Unfiltered message
 	 * @return string Message with no signature
 	 */
-	private static function removeSig(string $message): string
+	private static function removeSig(string $message): array
 	{
 		$sigpos = strrpos($message, "\n-- \n");
 		$quotepos = strrpos($message, "[/quote]");
@@ -662,7 +663,7 @@ class Email
 		return implode("\n", $lines);
 	}
 
-	private static function convertQuote(strng $body, string $reply): string
+	private static function convertQuote(string $body, string $reply): string
 	{
 		// Convert Quotes
 		$arrbody = explode("\n", trim($body));
diff --git a/src/Util/XML.php b/src/Util/XML.php
index 0424400a82..e87122dc7c 100644
--- a/src/Util/XML.php
+++ b/src/Util/XML.php
@@ -42,9 +42,9 @@ class XML
 	 * @param bool   $remove_header Should the XML header be removed or not?
 	 * @param array  $namespaces    List of namespaces
 	 * @param bool   $root          interally used parameter. Mustn't be used from outside.
-	 * @return void
+	 * @return string
 	 */
-	public static function fromArray(array $array, &$xml, bool $remove_header = false, array $namespaces = [], bool $root = true)
+	public static function fromArray(array $array, &$xml, bool $remove_header = false, array $namespaces = [], bool $root = true): string
 	{
 		if ($root) {
 			foreach ($array as $key => $value) {
@@ -130,6 +130,7 @@ class XML
 				self::fromArray($value, $element, $remove_header, $namespaces, false);
 			}
 		}
+		return '';
 	}
 
 	/**
@@ -142,7 +143,7 @@ class XML
 	 */
 	public static function copy(&$source, &$target, string $elementname)
 	{
-		if (count($source->children()) == 0) {
+		if (is_string($source) && count($source->children()) == 0) {
 			$target->addChild($elementname, self::escape($source));
 		} else {
 			$child = $target->addChild($elementname);
@@ -184,9 +185,9 @@ class XML
 	 * @param array       $attributes Array containing the attributes
 	 * @return void
 	 */
-	public static function addElement(DOMDocument $doc, DOMElement &$parent, string $element, string $value = '', array $attributes = [])
+	public static function addElement(DOMDocument $doc, DOMElement &$parent, string $element, string $value = null, array $attributes = [])
 	{
-		$element = self::createElement($doc, $element, $value, $attributes);
+		$element = self::createElement($doc, $element, $value ?? '', $attributes);
 		$parent->appendChild($element);
 	}
 
@@ -273,6 +274,7 @@ class XML
 			return [];
 		}
 
+		$parent = [];
 
 		libxml_use_internal_errors(true);
 		libxml_clear_errors();