diff --git a/src/Contact/Avatar.php b/src/Contact/Avatar.php
index 60981485e8..f43ed7b8c7 100644
--- a/src/Contact/Avatar.php
+++ b/src/Contact/Avatar.php
@@ -123,7 +123,7 @@ class Avatar
 		return $fields;
 	}
 
-	private static function getFilename(string $url)
+	private static function getFilename(string $url): string
 	{
 		$guid = Item::guidFromUri($url, parse_url($url, PHP_URL_HOST));
 
diff --git a/src/Content/BoundariesPager.php b/src/Content/BoundariesPager.php
index 358539794c..a8b873f22a 100644
--- a/src/Content/BoundariesPager.php
+++ b/src/Content/BoundariesPager.php
@@ -49,7 +49,7 @@ class BoundariesPager extends Pager
 	 * @param string  $last_item_id  The id† of the last item in the displayed item list
 	 * @param integer $itemsPerPage  An optional number of items per page to override the default value
 	 */
-	public function __construct(L10n $l10n, $queryString, $first_item_id = null, $last_item_id = null, $itemsPerPage = 50)
+	public function __construct(L10n $l10n, string $queryString, string $first_item_id = null, string $last_item_id = null, int $itemsPerPage = 50)
 	{
 		parent::__construct($l10n, $queryString, $itemsPerPage);
 
@@ -102,7 +102,7 @@ class BoundariesPager extends Pager
 	 * @return string HTML string of the pager
 	 * @throws \Exception
 	 */
-	public function renderMinimal(int $itemCount)
+	public function renderMinimal(int $itemCount): string
 	{
 		$displayedItemCount = max(0, intval($itemCount));
 
diff --git a/src/Content/ContactSelector.php b/src/Content/ContactSelector.php
index 6c7e09945f..fd574889e6 100644
--- a/src/Content/ContactSelector.php
+++ b/src/Content/ContactSelector.php
@@ -41,7 +41,7 @@ class ContactSelector
 	 * @param boolean $disabled optional, default false
 	 * @return string
 	 */
-	public static function pollInterval($current, $disabled = false)
+	public static function pollInterval(string $current, bool $disabled = false): string
 	{
 		$dis = (($disabled) ? ' disabled="disabled" ' : '');
 		$o = '';
@@ -84,7 +84,7 @@ class ContactSelector
 	 * @return string Server URL
 	 * @throws \Exception
 	 */
-	private static function getServerURLForProfile($profile)
+	private static function getServerURLForProfile(string $profile): string
 	{
 		if (!empty(self::$server_url[$profile])) {
 			return self::$server_url[$profile];
@@ -114,10 +114,11 @@ class ContactSelector
 	 * @param string $network  network of the contact
 	 * @param string $profile  optional, default empty
 	 * @param string $protocol (Optional) Protocol that is used for the transmission
+	 * @param int $gsid ??? (@TODO)
 	 * @return string
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	public static function networkToName($network, $profile = '', $protocol = '', $gsid = 0)
+	public static function networkToName(string $network, string $profile = '', string $protocol = '', int $gsid = 0): string
 	{
 		$nets = [
 			Protocol::DFRN      =>   DI::l10n()->t('DFRN'),
@@ -181,10 +182,11 @@ class ContactSelector
 	/**
 	 * @param string $network network
 	 * @param string $profile optional, default empty
+	 * @param int $gsid ??? (@TODO)
 	 * @return string
 	 * @throws \Exception
 	 */
-	public static function networkToIcon($network, $profile = "", $gsid = 0)
+	public static function networkToIcon(string $network, string $profile = "", int $gsid = 0): string
 	{
 		$nets = [
 			Protocol::DFRN      =>   'friendica',
diff --git a/src/Content/Conversation.php b/src/Content/Conversation.php
index 952b80e768..1088497983 100644
--- a/src/Content/Conversation.php
+++ b/src/Content/Conversation.php
@@ -189,7 +189,7 @@ class Conversation
 	 * @return string formatted text
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	public function formatActivity(array $links, $verb, $id)
+	public function formatActivity(array $links, string $verb, int $id): string
 	{
 		$this->profiler->startRecording('rendering');
 		$o        = '';
@@ -275,7 +275,7 @@ class Conversation
 		return $o;
 	}
 
-	public function statusEditor(array $x = [], $notes_cid = 0, $popup = false)
+	public function statusEditor(array $x = [], int $notes_cid = 0, bool $popup = false): string
 	{
 		$user = User::getById($this->app->getLoggedInUserId(), ['uid', 'nickname', 'allow_location', 'default-location']);
 		if (empty($user['uid'])) {
@@ -414,8 +414,8 @@ class Conversation
 	 * figures out how to determine page owner and other contextual items
 	 * that are based on unique features of the calling module.
 	 * @param array  $items
-	 * @param        $mode
-	 * @param        $update
+	 * @param string $mode
+	 * @param        $update @TODO Which type?
 	 * @param bool   $preview
 	 * @param string $order
 	 * @param int    $uid
@@ -423,7 +423,7 @@ class Conversation
 	 * @throws ImagickException
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	public function create(array $items, $mode, $update, $preview = false, $order = 'commented', $uid = 0)
+	public function create(array $items, string $mode, $update, bool $preview = false, string $order = 'commented', int $uid = 0): string
 	{
 		$this->profiler->startRecording('rendering');
 
@@ -784,7 +784,7 @@ class Conversation
 		return $o;
 	}
 
-	private function getBlocklist()
+	private function getBlocklist(): array
 	{
 		if (!local_user()) {
 			return [];
@@ -816,7 +816,7 @@ class Conversation
 	 *
 	 * @return array items with parents and comments
 	 */
-	private function addRowInformation(array $row, array $activity, array $thr_parent)
+	private function addRowInformation(array $row, array $activity, array $thr_parent): array
 	{
 		$this->profiler->startRecording('rendering');
 
@@ -911,7 +911,7 @@ class Conversation
 	 * @return array items with parents and comments
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	private function addChildren(array $parents, bool $block_authors, string $order, int $uid, string $mode)
+	private function addChildren(array $parents, bool $block_authors, string $order, int $uid, string $mode): array
 	{
 		$this->profiler->startRecording('rendering');
 		if (count($parents) > 1) {
@@ -1005,7 +1005,7 @@ class Conversation
 	 * @param bool  $recursive
 	 * @return array
 	 */
-	private function getItemChildren(array &$item_list, array $parent, $recursive = true)
+	private function getItemChildren(array &$item_list, array $parent, bool $recursive = true): array
 	{
 		$this->profiler->startRecording('rendering');
 		$children = [];
@@ -1040,7 +1040,7 @@ class Conversation
 	 * @param array $items
 	 * @return array
 	 */
-	private function sortItemChildren(array $items)
+	private function sortItemChildren(array $items): array
 	{
 		$this->profiler->startRecording('rendering');
 		$result = $items;
@@ -1086,7 +1086,7 @@ class Conversation
 	 * @param array $parent A tree-like array of items
 	 * @return array
 	 */
-	private function smartFlattenConversation(array $parent)
+	private function smartFlattenConversation(array $parent): array
 	{
 		$this->profiler->startRecording('rendering');
 		if (!isset($parent['children']) || count($parent['children']) == 0) {
@@ -1142,7 +1142,7 @@ class Conversation
 	 * @return array
 	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 	 */
-	private function convSort(array $item_list, $order)
+	private function convSort(array $item_list, string $order): array
 	{
 		$this->profiler->startRecording('rendering');
 		$parents = [];
@@ -1222,7 +1222,7 @@ class Conversation
 	 * @param array $b
 	 * @return int
 	 */
-	private function sortThrFeaturedReceived(array $a, array $b)
+	private function sortThrFeaturedReceived(array $a, array $b): int
 	{
 		if ($b['featured'] && !$a['featured']) {
 			return 1;
@@ -1240,7 +1240,7 @@ class Conversation
 	 * @param array $b
 	 * @return int
 	 */
-	private function sortThrFeaturedCommented(array $a, array $b)
+	private function sortThrFeaturedCommented(array $a, array $b): int
 	{
 		if ($b['featured'] && !$a['featured']) {
 			return 1;
@@ -1258,7 +1258,7 @@ class Conversation
 	 * @param array $b
 	 * @return int
 	 */
-	private function sortThrReceived(array $a, array $b)
+	private function sortThrReceived(array $a, array $b): int
 	{
 		return strcmp($b['received'], $a['received']);
 	}
@@ -1270,7 +1270,7 @@ class Conversation
 	 * @param array $b
 	 * @return int
 	 */
-	private function sortThrReceivedRev(array $a, array $b)
+	private function sortThrReceivedRev(array $a, array $b): int
 	{
 		return strcmp($a['received'], $b['received']);
 	}
@@ -1282,7 +1282,7 @@ class Conversation
 	 * @param array $b
 	 * @return int
 	 */
-	private function sortThrCommented(array $a, array $b)
+	private function sortThrCommented(array $a, array $b): int
 	{
 		return strcmp($b['commented'], $a['commented']);
 	}
@@ -1294,7 +1294,7 @@ class Conversation
 	 * @param array $b
 	 * @return int
 	 */
-	private function sortThrCreated(array $a, array $b)
+	private function sortThrCreated(array $a, array $b): int
 	{
 		return strcmp($b['created'], $a['created']);
 	}
diff --git a/src/Model/Log/ParsedLogIterator.php b/src/Model/Log/ParsedLogIterator.php
index 711391cb01..d3a5650397 100644
--- a/src/Model/Log/ParsedLogIterator.php
+++ b/src/Model/Log/ParsedLogIterator.php
@@ -60,7 +60,7 @@ class ParsedLogIterator implements \Iterator
 	 * @param string $filename	File to open
 	 * @return $this
 	 */
-	public function open(string $filename)
+	public function open(string $filename): ParsedLogIterator
 	{
 		$this->reader->open($filename);
 		return $this;
@@ -70,7 +70,7 @@ class ParsedLogIterator implements \Iterator
 	 * @param int $limit		Max num of lines to read
 	 * @return $this
 	 */
-	public function withLimit(int $limit)
+	public function withLimit(int $limit): ParsedLogIterator
 	{
 		$this->limit = $limit;
 		return $this;
@@ -80,7 +80,7 @@ class ParsedLogIterator implements \Iterator
 	 * @param array $filters		filters per column
 	 * @return $this
 	 */
-	public function withFilters(array $filters)
+	public function withFilters(array $filters): ParsedLogIterator
 	{
 		$this->filters = $filters;
 		return $this;
@@ -90,7 +90,7 @@ class ParsedLogIterator implements \Iterator
 	 * @param string $search	string to search to filter lines
 	 * @return $this
 	 */
-	public function withSearch(string $search)
+	public function withSearch(string $search): ParsedLogIterator
 	{
 		$this->search = $search;
 		return $this;
@@ -100,10 +100,10 @@ class ParsedLogIterator implements \Iterator
 	 * Check if parsed log line match filters.
 	 * Always match if no filters are set.
 	 *
-	 * @param ParsedLogLine $parsedlogline
-	 * @return bool
+	 * @param ParsedLogLine $parsedlogline ParsedLogLine instance
+	 * @return bool Wether the parse log line matches
 	 */
-	private function filter($parsedlogline)
+	private function filter(ParsedLogLine $parsedlogline): bool
 	{
 		$match = true;
 		foreach ($this->filters as $filter => $filtervalue) {
@@ -126,7 +126,7 @@ class ParsedLogIterator implements \Iterator
 	 * @param ParsedLogLine $parsedlogline
 	 * @return bool
 	 */
-	private function search($parsedlogline)
+	private function search(ParsedLogLine $parsedlogline): bool
 	{
 		if ($this->search != "") {
 			return strstr($parsedlogline->logline, $this->search) !== false;
diff --git a/src/Profile/ProfileField/Collection/ProfileFields.php b/src/Profile/ProfileField/Collection/ProfileFields.php
index 0520103d76..906b690fa2 100644
--- a/src/Profile/ProfileField/Collection/ProfileFields.php
+++ b/src/Profile/ProfileField/Collection/ProfileFields.php
@@ -33,9 +33,9 @@ class ProfileFields extends BaseCollection
 
 	/**
 	 * @param callable $callback
-	 * @return ProfileFields
+	 * @return ProfileFields (as an extended form of BaseCollection)
 	 */
-	public function map(callable $callback): ProfileFields
+	public function map(callable $callback): BaseCollection
 	{
 		return parent::map($callback);
 	}