diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index ec53bf567..755ca4148 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -125,21 +125,11 @@ parameters:
 			count: 1
 			path: program/actions/contacts/index.php
 
-		-
-			message: "#^Call to function is_object\\(\\) with rcube_result_set will always evaluate to true\\.$#"
-			count: 1
-			path: program/actions/contacts/mailto.php
-
 		-
 			message: "#^Access to an undefined property rcube_addressbook\\:\\:\\$deletable\\.$#"
 			count: 1
 			path: program/actions/contacts/move.php
 
-		-
-			message: "#^Left side of && is always true\\.$#"
-			count: 1
-			path: program/actions/contacts/photo.php
-
 		-
 			message: "#^Right side of && is always true\\.$#"
 			count: 1
@@ -155,11 +145,6 @@ parameters:
 			count: 1
 			path: program/actions/contacts/save.php
 
-		-
-			message: "#^Right side of && is always true\\.$#"
-			count: 1
-			path: program/actions/contacts/save.php
-
 		-
 			message: "#^Implicit array creation is not allowed \\- variable \\$fields might not exist\\.$#"
 			count: 1
@@ -175,11 +160,6 @@ parameters:
 			count: 1
 			path: program/actions/mail/attachment_upload.php
 
-		-
-			message: "#^If condition is always true\\.$#"
-			count: 1
-			path: program/actions/mail/autocomplete.php
-
 		-
 			message: "#^Access to an undefined property rcube_message\\:\\:\\$size\\.$#"
 			count: 1
@@ -525,76 +505,6 @@ parameters:
 			count: 2
 			path: program/include/rcmail_sendmail.php
 
-		-
-			message: "#^Method rcmail_string_replacer\\:\\:mailto_callback\\(\\) should return int but returns string\\.$#"
-			count: 1
-			path: program/include/rcmail_string_replacer.php
-
-		-
-			message: "#^Return type \\(int\\) of method rcmail_string_replacer\\:\\:mailto_callback\\(\\) should be compatible with return type \\(string\\) of method rcube_string_replacer\\:\\:mailto_callback\\(\\)$#"
-			count: 1
-			path: program/include/rcmail_string_replacer.php
-
-		-
-			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
-			count: 2
-			path: program/lib/Roundcube/bootstrap.php
-
-		-
-			message: "#^Call to function is_array\\(\\) with non\\-empty\\-array will always evaluate to true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/bootstrap.php
-
-		-
-			message: "#^Call to function is_string\\(\\) with string will always evaluate to true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/bootstrap.php
-
-		-
-			message: "#^Function array_first\\(\\) should return mixed but return statement is missing\\.$#"
-			count: 1
-			path: program/lib/Roundcube/bootstrap.php
-
-		-
-			message: "#^Function parse_bytes\\(\\) never returns null so it can be removed from the return type\\.$#"
-			count: 1
-			path: program/lib/Roundcube/bootstrap.php
-
-		-
-			message: "#^Result of \\|\\| is always false\\.$#"
-			count: 1
-			path: program/lib/Roundcube/bootstrap.php
-
-		-
-			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
-			count: 2
-			path: program/lib/Roundcube/html.php
-
-		-
-			message: "#^Call to function is_string\\(\\) with array will always evaluate to false\\.$#"
-			count: 2
-			path: program/lib/Roundcube/html.php
-
-		-
-			message: "#^Call to function is_string\\(\\) with string will always evaluate to true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/html.php
-
-		-
-			message: "#^html_hiddenfield\\:\\:__construct\\(\\) does not call parent constructor from html\\.$#"
-			count: 1
-			path: program/lib/Roundcube/html.php
-
-		-
-			message: "#^html_inputfield\\:\\:__construct\\(\\) does not call parent constructor from html\\.$#"
-			count: 1
-			path: program/lib/Roundcube/html.php
-
-		-
-			message: "#^html_table\\:\\:__construct\\(\\) does not call parent constructor from html\\.$#"
-			count: 1
-			path: program/lib/Roundcube/html.php
-
 		-
 			message: "#^Access to an undefined property rcube\\:\\:\\$password\\.$#"
 			count: 1
@@ -680,56 +590,6 @@ parameters:
 			count: 1
 			path: program/lib/Roundcube/rcube.php
 
-		-
-			message: "#^Comparison operation \"\\>\" between int\\<1, max\\> and 0 is always true\\.$#"
-			count: 2
-			path: program/lib/Roundcube/rcube_addressbook.php
-
-		-
-			message: "#^Instanceof between rcube_result_set and rcube_result_set will always evaluate to true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addressbook.php
-
-		-
-			message: "#^Method rcube_addressbook\\:\\:insert\\(\\) should return mixed but return statement is missing\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addressbook.php
-
-		-
-			message: "#^Method rcube_addressbook\\:\\:update\\(\\) should return mixed but return statement is missing\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addressbook.php
-
-		-
-			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
-			count: 2
-			path: program/lib/Roundcube/rcube_addresses.php
-
-		-
-			message: "#^Left side of && is always true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addresses.php
-
-		-
-			message: "#^Method rcube_addresses\\:\\:list_records\\(\\) should return array but returns rcube_result_set\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addresses.php
-
-		-
-			message: "#^Return type \\(array\\) of method rcube_addresses\\:\\:list_records\\(\\) should be compatible with return type \\(rcube_result_set\\) of method rcube_contacts\\:\\:list_records\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addresses.php
-
-		-
-			message: "#^Right side of && is always true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addresses.php
-
-		-
-			message: "#^rcube_addresses\\:\\:__construct\\(\\) does not call parent constructor from rcube_contacts\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_addresses.php
-
 		-
 			message: "#^Foreach overwrites \\$key with its value variable\\.$#"
 			count: 1
@@ -755,46 +615,6 @@ parameters:
 			count: 1
 			path: program/lib/Roundcube/rcube_charset.php
 
-		-
-			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
-			count: 3
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^Foreach overwrites \\$value with its value variable\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^If condition is always true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^Left side of && is always true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^Parameter \\#1 \\$cols \\(array\\) of method rcube_contacts\\:\\:list_records\\(\\) should be contravariant with parameter \\$cols \\(array\\|null\\) of method rcube_addressbook\\:\\:list_records\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^Parameter \\#1 \\$filter \\(string\\) of method rcube_contacts\\:\\:set_search_set\\(\\) should be contravariant with parameter \\$filter \\(mixed\\) of method rcube_addressbook\\:\\:set_search_set\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^Parameter \\#1 \\$search \\(string\\) of method rcube_contacts\\:\\:list_groups\\(\\) should be contravariant with parameter \\$search \\(string\\|null\\) of method rcube_addressbook\\:\\:list_groups\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
-		-
-			message: "#^Return type \\(mixed\\) of method rcube_contacts\\:\\:get_result\\(\\) should be covariant with return type \\(rcube_result_set\\|null\\) of method rcube_addressbook\\:\\:get_result\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_contacts.php
-
 		-
 			message: "#^Left side of && is always true\\.$#"
 			count: 2
@@ -805,86 +625,6 @@ parameters:
 			count: 1
 			path: program/lib/Roundcube/rcube_html2text.php
 
-		-
-			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Call to function is_array\\(\\) with mixed will always evaluate to false\\.$#"
-			count: 2
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Method rcube_ldap\\:\\:rename_group\\(\\) should return bool but returns string\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Offset '%%dn' on non\\-empty\\-array in empty\\(\\) always exists and is not falsy\\.$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Parameter \\#1 \\$cols \\(array\\) of method rcube_ldap\\:\\:list_records\\(\\) should be contravariant with parameter \\$cols \\(array\\|null\\) of method rcube_addressbook\\:\\:list_records\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Parameter \\#1 \\$filter \\(string\\) of method rcube_ldap\\:\\:set_search_set\\(\\) should be contravariant with parameter \\$filter \\(mixed\\) of method rcube_addressbook\\:\\:set_search_set\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Parameter \\#1 \\$search \\(string\\) of method rcube_ldap\\:\\:list_groups\\(\\) should be contravariant with parameter \\$search \\(string\\|null\\) of method rcube_addressbook\\:\\:list_groups\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Parameter \\#1 \\$sort_col \\(string\\) of method rcube_ldap\\:\\:set_sort_order\\(\\) should be contravariant with parameter \\$sort_col \\(string\\|null\\) of method rcube_addressbook\\:\\:set_sort_order\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Parameter \\#2 \\$sort_order \\(string\\) of method rcube_ldap\\:\\:set_sort_order\\(\\) should be contravariant with parameter \\$sort_order \\(string\\|null\\) of method rcube_addressbook\\:\\:set_sort_order\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Parameter \\#6 \\$required \\(array\\) of method rcube_ldap\\:\\:search\\(\\) should be contravariant with parameter \\$required \\(array\\<string\\>\\|string\\) of method rcube_addressbook\\:\\:search\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Result of && is always false\\.$#"
-			count: 2
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Return type \\(bool\\) of method rcube_ldap\\:\\:rename_group\\(\\) should be covariant with return type \\(string\\|false\\) of method rcube_addressbook\\:\\:rename_group\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Return type \\(bool\\|int\\) of method rcube_ldap\\:\\:delete\\(\\) should be covariant with return type \\(int\\|false\\) of method rcube_addressbook\\:\\:delete\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Return type \\(mixed\\) of method rcube_ldap\\:\\:create_group\\(\\) should be covariant with return type \\(array\\|false\\) of method rcube_addressbook\\:\\:create_group\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Return type \\(mixed\\) of method rcube_ldap\\:\\:get_record\\(\\) should be covariant with return type \\(array\\|rcube_result_set\\) of method rcube_addressbook\\:\\:get_record\\(\\)$#"
-			count: 1
-			path: program/lib/Roundcube/rcube_ldap.php
-
-		-
-			message: "#^Right side of && is always true\\.$#"
-			count: 3
-			path: program/lib/Roundcube/rcube_ldap.php
-
 		-
 			message: "#^Call to function is_array\\(\\) with array will always evaluate to true\\.$#"
 			count: 1
diff --git a/program/actions/contacts/mailto.php b/program/actions/contacts/mailto.php
index e19da5fca..6d044f08e 100644
--- a/program/actions/contacts/mailto.php
+++ b/program/actions/contacts/mailto.php
@@ -65,7 +65,7 @@ class rcmail_action_contacts_mailto extends rcmail_action_contacts_index
         }
 
         foreach ($sources as $source) {
-            while (is_object($source) && ($rec = $source->iterate())) {
+            foreach ($source as $rec) {
                 $emails = rcube_addressbook::get_col_values('email', $rec, true);
 
                 if (!empty($emails)) {
diff --git a/program/actions/contacts/photo.php b/program/actions/contacts/photo.php
index a1c8b516b..31b1f15ad 100644
--- a/program/actions/contacts/photo.php
+++ b/program/actions/contacts/photo.php
@@ -54,7 +54,7 @@ class rcmail_action_contacts_photo extends rcmail_action_contacts_index
                 foreach ($rcmail->get_address_sources() as $s) {
                     $abook = $rcmail->get_address_book($s['id']);
                     $result = $abook->search(['email'], $email, 1, true, true, 'photo');
-                    while ($result && ($record = $result->iterate())) {
+                    foreach ($result as $record) {
                         if (!empty($record['photo'])) {
                             break 2;
                         }
diff --git a/program/actions/contacts/save.php b/program/actions/contacts/save.php
index da2a10661..44f85bf16 100644
--- a/program/actions/contacts/save.php
+++ b/program/actions/contacts/save.php
@@ -154,9 +154,12 @@ class rcmail_action_contacts_save extends rcmail_action_contacts_index
 
             // show notice if existing contacts with same e-mail are found
             foreach ($contacts->get_col_values('email', $a_record, true) as $email) {
-                if ($email && ($res = $contacts->search('email', $email, 1, false, true)) && $res->count) {
-                    $rcmail->output->show_message('contactexists', 'notice', null, false);
-                    break;
+                if ($email) {
+                    $res = $contacts->search('email', $email, 1, false, true);
+                    if ($res->count) {
+                        $rcmail->output->show_message('contactexists', 'notice', null, false);
+                        break;
+                    }
                 }
             }
 
diff --git a/program/actions/mail/autocomplete.php b/program/actions/mail/autocomplete.php
index 9d9c8e9a8..b28d267bd 100644
--- a/program/actions/mail/autocomplete.php
+++ b/program/actions/mail/autocomplete.php
@@ -49,9 +49,10 @@ class rcmail_action_mail_autocomplete extends rcmail_action
             foreach ($book_types as $abook_id) {
                 $abook = $rcmail->get_address_book($abook_id);
                 $abook->set_pagesize($MAXNUM);
+                $result = $abook->search($fields, $search, $mode, true, true, 'email');
 
-                if ($result = $abook->search($fields, $search, $mode, true, true, 'email')) {
-                    while ($record = $result->iterate()) {
+                if ($result->count) {
+                    foreach ($result as $record) {
                         // Contact can have more than one e-mail address
                         $email_arr = (array) $abook->get_col_values('email', $record, true);
                         $email_cnt = count($email_arr);
diff --git a/program/include/rcmail_string_replacer.php b/program/include/rcmail_string_replacer.php
index dab502942..708b8cd82 100644
--- a/program/include/rcmail_string_replacer.php
+++ b/program/include/rcmail_string_replacer.php
@@ -30,7 +30,7 @@ class rcmail_string_replacer extends rcube_string_replacer
      *
      * @param array $matches Matches result from preg_replace_callback
      *
-     * @return int Index of saved string value
+     * @return string Replacement string
      *
      * @see rcube_string_replacer::mailto_callback()
      */
diff --git a/program/lib/Roundcube/bootstrap.php b/program/lib/Roundcube/bootstrap.php
index 2c68fb5ba..d4657924b 100644
--- a/program/lib/Roundcube/bootstrap.php
+++ b/program/lib/Roundcube/bootstrap.php
@@ -115,16 +115,12 @@ if (class_exists('PEAR')) {
  * Similar function as in_array() but case-insensitive with multibyte support.
  *
  * @param string $needle   Needle value
- * @param array  $haystack Array to search in
+ * @param ?array $haystack Array to search in
  *
  * @return bool True if found, False if not
  */
 function in_array_nocase($needle, $haystack)
 {
-    if (!is_string($needle) || !is_array($haystack)) {
-        return false;
-    }
-
     // use much faster method for ascii
     if (is_ascii($needle)) {
         foreach ((array) $haystack as $value) {
@@ -147,9 +143,9 @@ function in_array_nocase($needle, $haystack)
 /**
  * Parse a human readable string for a number of bytes.
  *
- * @param string $str Input string
+ * @param string|int|float $str Input string
  *
- * @return int|false|null Number of bytes
+ * @return int|false Number of bytes
  */
 function parse_bytes($str)
 {
@@ -200,7 +196,7 @@ function unslashify($str)
 /**
  * Returns number of seconds for a specified offset string.
  *
- * @param string $str String representation of the offset (e.g. 20min, 5h, 2days, 1week)
+ * @param string|int $str String representation of the offset (e.g. 20min, 5h, 2days, 1week)
  *
  * @return int Number of seconds
  */
@@ -284,7 +280,8 @@ function array_keys_recursive($array)
 {
     $keys = [];
 
-    if (!empty($array) && is_array($array)) {
+    // @phpstan-ignore-next-line
+    if (is_array($array)) {
         foreach ($array as $key => $child) {
             $keys[] = $key;
             foreach (array_keys_recursive($child) as $val) {
@@ -305,12 +302,15 @@ function array_keys_recursive($array)
  */
 function array_first($array)
 {
-    if (is_array($array)) {
+    // @phpstan-ignore-next-line
+    if (is_array($array) && !empty($array)) {
         reset($array);
         foreach ($array as $element) {
             return $element;
         }
     }
+
+    return null;
 }
 
 /**
diff --git a/program/lib/Roundcube/html.php b/program/lib/Roundcube/html.php
index f15da76f6..5d222318c 100644
--- a/program/lib/Roundcube/html.php
+++ b/program/lib/Roundcube/html.php
@@ -40,6 +40,7 @@ class html
      */
     public function __construct($attrib = [])
     {
+        // @phpstan-ignore-next-line
         if (is_array($attrib)) {
             $this->attrib = $attrib;
         }
@@ -60,10 +61,10 @@ class html
     /**
      * Generic method to create a HTML tag
      *
-     * @param string $tagname Tag name
-     * @param array  $attrib  Tag attributes as key/value pairs
-     * @param string $content Optional Tag content (creates a container tag)
-     * @param array  $allowed List with allowed attributes, omit to allow all
+     * @param string       $tagname Tag name
+     * @param array|string $attrib  Tag attributes as key/value pairs, or 'class' attribute value
+     * @param string       $content Optional Tag content (creates a container tag)
+     * @param array        $allowed List with allowed attributes, omit to allow all
      *
      * @return string The XHTML tag
      */
@@ -387,13 +388,8 @@ class html
      *
      * @return string The quoted string
      */
-    public static function quote($str)
+    public static function quote(string $str)
     {
-        // PHP8 does not like e.g. an array as htmlspecialchars() argument
-        if (!is_string($str)) {
-            return (string) $str;
-        }
-
         return @htmlspecialchars($str, \ENT_COMPAT | \ENT_SUBSTITUTE, RCUBE_CHARSET);
     }
 }
@@ -419,9 +415,7 @@ class html_inputfield extends html
      */
     public function __construct($attrib = [])
     {
-        if (is_array($attrib)) {
-            $this->attrib = $attrib;
-        }
+        parent::__construct($attrib);
 
         if (!empty($attrib['type'])) {
             $this->type = $attrib['type'];
@@ -479,6 +473,8 @@ class html_hiddenfield extends html
      */
     public function __construct($attrib = null)
     {
+        parent::__construct();
+
         if (is_array($attrib)) {
             $this->add($attrib);
         }
@@ -710,8 +706,11 @@ class html_table extends html
      */
     public function __construct($attrib = [])
     {
-        $default_attrib = self::$doctype == 'xhtml' ? ['border' => '0'] : [];
-        $this->attrib = array_merge($attrib, $default_attrib);
+        parent::__construct($attrib);
+
+        if (self::$doctype == 'xhtml') {
+            $this->attrib['border'] = '0';
+        }
 
         if (!empty($attrib['tagname']) && $attrib['tagname'] != 'table') {
             $this->tagname = $attrib['tagname'];
@@ -722,8 +721,8 @@ class html_table extends html
     /**
      * Add a table cell
      *
-     * @param array  $attr Cell attributes
-     * @param string $cont Cell content
+     * @param array|string $attr Cell attributes or 'class' attribute value
+     * @param string       $cont Cell content
      */
     public function add($attr, $cont)
     {
diff --git a/program/lib/Roundcube/rcube_addressbook.php b/program/lib/Roundcube/rcube_addressbook.php
index 2155dc421..0c0a94d22 100644
--- a/program/lib/Roundcube/rcube_addressbook.php
+++ b/program/lib/Roundcube/rcube_addressbook.php
@@ -259,7 +259,7 @@ abstract class rcube_addressbook
      * @param mixed $id    Record identifier(s)
      * @param bool  $assoc True to return record as associative array, otherwise a result set is returned
      *
-     * @return rcube_result_set|array Result object with all record fields
+     * @return rcube_result_set|array|null Result object with all record fields
      */
     abstract public function get_record($id, $assoc = false);
 
@@ -316,7 +316,7 @@ abstract class rcube_addressbook
      * @param ?string $sort_col   Sort column
      * @param ?string $sort_order Sort order
      */
-    public function set_sort_order($sort_col, $sort_order = null)
+    public function set_sort_order($sort_col = null, $sort_order = null)
     {
         if ($sort_col && (array_key_exists($sort_col, $this->coltypes) || in_array($sort_col, $this->coltypes))) {
             $this->sort_col = $sort_col;
@@ -384,6 +384,7 @@ abstract class rcube_addressbook
     public function insert($save_data, $check = false)
     {
         // empty for read-only address books
+        return false;
     }
 
     /**
@@ -397,6 +398,8 @@ abstract class rcube_addressbook
     public function insertMultiple($recset, $check = false)
     {
         $ids = [];
+
+        // @phpstan-ignore-next-line
         if ($recset instanceof rcube_result_set) {
             foreach ($recset as $row) {
                 if ($insert = $this->insert($row, $check)) {
@@ -421,13 +424,14 @@ abstract class rcube_addressbook
     public function update($id, $save_cols)
     {
         // empty for read-only address books
+        return false;
     }
 
     /**
      * Mark one or more contact records as deleted
      *
-     * @param array $ids   Record identifiers
-     * @param bool  $force Remove records irreversible (see self::undelete)
+     * @param array|string $ids   Record identifiers
+     * @param bool         $force Remove records irreversible (see self::undelete)
      *
      * @return int|false Number of removed records, False on failure
      */
@@ -440,7 +444,7 @@ abstract class rcube_addressbook
     /**
      * Unmark delete flag on contact record(s)
      *
-     * @param array $ids Record identifiers
+     * @param array|string $ids Record identifiers
      */
     public function undelete($ids)
     {
@@ -621,7 +625,7 @@ abstract class rcube_addressbook
 
         // remove duplicates
         if ($flat && !empty($out)) {
-            $out = array_unique($out);
+            $out = array_values(array_unique($out));
         }
 
         return $out;
@@ -740,7 +744,7 @@ abstract class rcube_addressbook
                 $fn = $org;
             }
             // ... email address
-            elseif (($email = self::get_col_values('email', $contact, true)) && count($email) > 0) {
+            elseif (($email = self::get_col_values('email', $contact, true)) && isset($email[0])) {
                 $fn = $email[0];
             }
         }
@@ -827,7 +831,7 @@ abstract class rcube_addressbook
         $key = $contact[$sort_col] ?? null;
 
         // add email to a key to not skip contacts with the same name (#1488375)
-        if (($email = self::get_col_values('email', $contact, true)) && count($email) > 0) {
+        if (($email = self::get_col_values('email', $contact, true)) && isset($email[0])) {
             $key .= ':' . implode(':', (array) $email);
         }
 
diff --git a/program/lib/Roundcube/rcube_addresses.php b/program/lib/Roundcube/rcube_addresses.php
index 46815a01a..e56e62e4c 100644
--- a/program/lib/Roundcube/rcube_addresses.php
+++ b/program/lib/Roundcube/rcube_addresses.php
@@ -45,10 +45,9 @@ class rcube_addresses extends rcube_contacts
      */
     public function __construct($dbconn, $user, $type)
     {
-        $this->db = $dbconn;
-        $this->user_id = $user;
+        parent::__construct($dbconn, $user);
+
         $this->type = $type;
-        $this->ready = $this->db && !$this->db->is_error();
     }
 
     /**
@@ -72,11 +71,11 @@ class rcube_addresses extends rcube_contacts
     /**
      * List the current set of contact records
      *
-     * @param array $cols    List of cols to show, Null means all
-     * @param int   $subset  Only return this number of records, use negative values for tail
-     * @param bool  $nocount True to skip the count query (select only)
+     * @param ?array $cols    List of cols to show, Null means all
+     * @param int    $subset  Only return this number of records, use negative values for tail
+     * @param bool   $nocount True to skip the count query (select only)
      *
-     * @return array Indexed list of contact records, each a hash array
+     * @return rcube_result_set Indexed list of contact records, each a hash array
      */
     public function list_records($cols = null, $subset = 0, $nocount = false)
     {
@@ -241,7 +240,7 @@ class rcube_addresses extends rcube_contacts
      * @param mixed $id    Record identifier(s)
      * @param bool  $assoc Enables returning associative array
      *
-     * @return rcube_result_set|array Result object with all record fields
+     * @return rcube_result_set|array|null Result object with all record fields
      */
     public function get_record($id, $assoc = false)
     {
@@ -306,15 +305,12 @@ class rcube_addresses extends rcube_contacts
      * @param array $save_data Associative array with save data
      * @param bool  $check     Enables validity checks
      *
-     * @return int|bool The created record ID on success, False on error
+     * @return mixed The created record ID on success, False on error
      */
     public function insert($save_data, $check = false)
     {
-        if (!is_array($save_data)) {
-            return false;
-        }
-
-        if ($check && ($existing = $this->search('email', $save_data['email'], false, false))) {
+        if ($check) {
+            $existing = $this->search('email', $save_data['email'], false, false);
             if ($existing->count) {
                 return false;
             }
@@ -351,8 +347,8 @@ class rcube_addresses extends rcube_contacts
     /**
      * Delete one or more contact records
      *
-     * @param array $ids   Record identifiers
-     * @param bool  $force Remove record(s) irreversible (unsupported)
+     * @param array|string $ids   Record identifiers as an array or a string with self::SEPARATOR
+     * @param bool         $force Remove record(s) irreversible (unsupported)
      *
      * @return int|false Number of removed records
      */
diff --git a/program/lib/Roundcube/rcube_contacts.php b/program/lib/Roundcube/rcube_contacts.php
index a2554e714..ab364c807 100644
--- a/program/lib/Roundcube/rcube_contacts.php
+++ b/program/lib/Roundcube/rcube_contacts.php
@@ -71,7 +71,7 @@ class rcube_contacts extends rcube_addressbook
     {
         $this->db = $dbconn;
         $this->user_id = $user;
-        $this->ready = $this->db && !$this->db->is_error();
+        $this->ready = !$this->db->is_error();
     }
 
     /**
@@ -87,7 +87,7 @@ class rcube_contacts extends rcube_addressbook
     /**
      * Save a search string for future listings
      *
-     * @param string $filter SQL params to use in listing method
+     * @param mixed $filter SQL params to use in listing method
      */
     public function set_search_set($filter): void
     {
@@ -128,8 +128,8 @@ class rcube_contacts extends rcube_addressbook
     /**
      * List all active contact groups of this source
      *
-     * @param string $search Search string to match group name
-     * @param int    $mode   Matching mode. Sum of rcube_addressbook::SEARCH_*
+     * @param ?string $search Search string to match group name
+     * @param int     $mode   Matching mode. Sum of rcube_addressbook::SEARCH_*
      *
      * @return array Indexed list of contact groups, each a hash array
      */
@@ -196,9 +196,9 @@ class rcube_contacts extends rcube_addressbook
     /**
      * List the current set of contact records
      *
-     * @param array $cols    List of cols to show, Null means all
-     * @param int   $subset  Only return this number of records, use negative values for tail
-     * @param bool  $nocount True to skip the count query (select only)
+     * @param ?array $cols    List of cols to show, Null means all
+     * @param int    $subset  Only return this number of records, use negative values for tail
+     * @param bool   $nocount True to skip the count query (select only)
      *
      * @return rcube_result_set Indexed list of contact records, each a hash array
      */
@@ -382,8 +382,8 @@ class rcube_contacts extends rcube_addressbook
                             $pos = strpos($col, ':');
                             $colname = $pos ? substr($col, 0, $pos) : $col;
                             $search = $post_search[$colname];
-                            foreach ((array) $row[$col] as $value) {
-                                if ($this->compare_search_value($colname, $value, $search, $mode)) {
+                            foreach ((array) $row[$col] as $_value) {
+                                if ($this->compare_search_value($colname, $_value, $search, $mode)) {
                                     $found[$colname] = true;
                                     break;
                                 }
@@ -425,7 +425,7 @@ class rcube_contacts extends rcube_addressbook
             // when we know we have an empty result
             if ($ids == '0') {
                 $this->set_search_set($where);
-                return $this->result = new rcube_result_set(0, 0);
+                return $this->result = new rcube_result_set();
             }
         }
 
@@ -436,6 +436,8 @@ class rcube_contacts extends rcube_addressbook
             } else {
                 $this->result = $this->count();
             }
+        } else {
+            return $this->result = new rcube_result_set();
         }
 
         return $this->result;
@@ -516,7 +518,7 @@ class rcube_contacts extends rcube_addressbook
     /**
      * Return the last result set
      *
-     * @return mixed Result array or NULL if nothing selected yet
+     * @return rcube_result_set|null Result array or NULL if nothing selected yet
      */
     public function get_result()
     {
@@ -529,7 +531,7 @@ class rcube_contacts extends rcube_addressbook
      * @param mixed $id    Record identifier(s)
      * @param bool  $assoc Enables returning associative array
      *
-     * @return rcube_result_set|array Result object with all record fields
+     * @return rcube_result_set|array|null Result object with all record fields
      */
     public function get_record($id, $assoc = false)
     {
@@ -624,21 +626,18 @@ class rcube_contacts extends rcube_addressbook
      * @param array $save_data Associative array with save data
      * @param bool  $check     Enables validity checks
      *
-     * @return int|bool The created record ID on success, False on error
+     * @return mixed The created record ID on success, False on error
      */
     public function insert($save_data, $check = false)
     {
-        if (!is_array($save_data)) {
-            return false;
-        }
-
         $insert_id = $existing = false;
 
         if ($check) {
             foreach ($save_data as $col => $values) {
                 if (strpos($col, 'email') === 0) {
                     foreach ((array) $values as $email) {
-                        if ($existing = $this->search('email', $email, false, false)) {
+                        $existing = $this->search('email', $email, false, false);
+                        if ($existing->count) {
                             break 2;
                         }
                     }
@@ -805,8 +804,8 @@ class rcube_contacts extends rcube_addressbook
     /**
      * Mark one or more contact records as deleted
      *
-     * @param array $ids   Record identifiers
-     * @param bool  $force Remove record(s) irreversible (unsupported)
+     * @param array|string $ids   Record identifiers array or string separated with self::SEPARATOR
+     * @param bool         $force Remove record(s) irreversible (unsupported)
      *
      * @return int|false Number of removed records, False on failure
      */
@@ -835,7 +834,7 @@ class rcube_contacts extends rcube_addressbook
     /**
      * Undelete one or more contact records
      *
-     * @param array $ids Record identifiers
+     * @param array|string $ids Record identifiers array or string separated with self::SEPARATOR
      *
      * @return int Number of undeleted contact records
      */
diff --git a/program/lib/Roundcube/rcube_ldap.php b/program/lib/Roundcube/rcube_ldap.php
index c6b28cce3..de2acd67e 100644
--- a/program/lib/Roundcube/rcube_ldap.php
+++ b/program/lib/Roundcube/rcube_ldap.php
@@ -436,6 +436,7 @@ class rcube_ldap extends rcube_addressbook
                         }
                     }
 
+                    // @phpstan-ignore-next-line
                     if ($this->cache && !empty($replaces['%dn'])) {
                         $this->cache->set($cache_key, $replaces['%dn']);
                     }
@@ -549,10 +550,10 @@ class rcube_ldap extends rcube_addressbook
     /**
      * Set internal sort settings
      *
-     * @param string $sort_col   Sort column
-     * @param string $sort_order Sort order
+     * @param ?string $sort_col   Sort column
+     * @param ?string $sort_order Sort order
      */
-    public function set_sort_order($sort_col, $sort_order = null)
+    public function set_sort_order($sort_col = null, $sort_order = null)
     {
         if (!empty($this->coltypes[$sort_col]['attributes'])) {
             $this->sort_col = $this->coltypes[$sort_col]['attributes'][0];
@@ -562,7 +563,7 @@ class rcube_ldap extends rcube_addressbook
     /**
      * Save a search string for future listings
      *
-     * @param string $filter Filter string
+     * @param mixed $filter Filter string
      */
     public function set_search_set($filter): void
     {
@@ -592,9 +593,9 @@ class rcube_ldap extends rcube_addressbook
     /**
      * List the current set of contact records
      *
-     * @param array $cols    List of cols to show
-     * @param int   $subset  Only return this number of records
-     * @param bool  $nocount True to skip the count query (Not used)
+     * @param ?array $cols    List of cols to show
+     * @param int    $subset  Only return this number of records
+     * @param bool   $nocount True to skip the count query (Not used)
      *
      * @return rcube_result_set Indexed list of contact records, each a hash array
      */
@@ -793,12 +794,12 @@ class rcube_ldap extends rcube_addressbook
     /**
      * Search contacts
      *
-     * @param mixed $fields   The field name of array of field names to search in
-     * @param mixed $value    Search value (or array of values when $fields is array)
-     * @param int   $mode     Matching mode. Sum of rcube_addressbook::SEARCH_*
-     * @param bool  $select   True if results are requested, False if count only
-     * @param bool  $nocount  (Not used)
-     * @param array $required List of fields that cannot be empty
+     * @param mixed                $fields   The field name of array of field names to search in
+     * @param mixed                $value    Search value (or array of values when $fields is array)
+     * @param int                  $mode     Matching mode. Sum of rcube_addressbook::SEARCH_*
+     * @param bool                 $select   True if results are requested, False if count only
+     * @param bool                 $nocount  (Not used)
+     * @param array<string>|string $required List of fields that cannot be empty, or a single field
      *
      * @return rcube_result_set List of contact records
      */
@@ -829,7 +830,7 @@ class rcube_ldap extends rcube_addressbook
         if (!empty($this->prop['vlv_search']) && $this->ready
             && implode(',', (array) $fields) == implode(',', $list_fields)
         ) {
-            $this->result = new rcube_result_set(0);
+            $this->result = new rcube_result_set();
 
             $this->ldap->config_set('fuzzy_search', $fuzzy_search);
 
@@ -1084,7 +1085,7 @@ class rcube_ldap extends rcube_addressbook
      * @param mixed $dn    Record identifier
      * @param bool  $assoc Return as associative array
      *
-     * @return mixed Hash array or rcube_result_set with all record fields
+     * @return array|rcube_result_set|null Hash array or rcube_result_set with all record fields
      */
     public function get_record($dn, $assoc = false)
     {
@@ -1178,19 +1179,19 @@ class rcube_ldap extends rcube_addressbook
                 // try to extract surname and firstname from displayname
                 $name_parts = preg_split('/[\s,.]+/', $save_data['name']);
 
-                if ($sn_field && $missing[$sn_field]) {
+                if ($sn_field && !empty($missing[$sn_field])) {
                     $save_data['surname'] = array_pop($name_parts);
                     unset($missing[$sn_field]);
                 }
 
-                if ($fn_field && $missing[$fn_field]) {
+                if ($fn_field && !empty($missing[$fn_field])) {
                     $save_data['firstname'] = array_shift($name_parts);
                     unset($missing[$fn_field]);
                 }
 
                 // try to fix missing e-mail, very often on import
                 // from vCard we have email:other only defined
-                if ($mail_field && $missing[$mail_field]) {
+                if ($mail_field && !empty($missing[$mail_field])) {
                     $emails = $this->get_col_values('email', $save_data, true);
                     if (!empty($emails) && ($email = array_first($emails))) {
                         $save_data['email'] = $email;
@@ -1320,9 +1321,11 @@ class rcube_ldap extends rcube_addressbook
                 }
                 // $this->_map_data() result and _raw_attrib use different format
                 // make sure comparing array with one element with a string works as expected
+                // @phpstan-ignore-next-line
                 if (is_array($old) && count($old) == 1 && !is_array($val)) {
                     $old = array_pop($old);
                 }
+                // @phpstan-ignore-next-line
                 if (is_array($val) && count($val) == 1 && !is_array($old)) {
                     $val = array_pop($val);
                 }
@@ -1464,10 +1467,10 @@ class rcube_ldap extends rcube_addressbook
     /**
      * Mark one or more contact records as deleted
      *
-     * @param array $ids   Record identifiers
-     * @param bool  $force Remove record(s) irreversible (unsupported)
+     * @param array|string $ids   Record identifiers array or comma-separated string
+     * @param bool         $force Remove record(s) irreversible (unsupported)
      *
-     * @return int|bool Number of deleted records on success, False on error
+     * @return int|false Number of deleted records on success, False on error
      */
     public function delete($ids, $force = true)
     {
@@ -1820,8 +1823,8 @@ class rcube_ldap extends rcube_addressbook
     /**
      * List all active contact groups of this source
      *
-     * @param string $search Optional search string to match group name
-     * @param int    $mode   Matching mode. Sum of rcube_addressbook::SEARCH_*
+     * @param ?string $search Optional search string to match group name
+     * @param int     $mode   Matching mode. Sum of rcube_addressbook::SEARCH_*
      *
      * @return array Indexed list of contact groups, each a hash array
      */
@@ -2038,7 +2041,7 @@ class rcube_ldap extends rcube_addressbook
      *
      * @param string $group_name The group name
      *
-     * @return mixed False on error, array with record props in success
+     * @return array|false False on error, array with record props in success
      */
     public function create_group($group_name)
     {
@@ -2096,7 +2099,7 @@ class rcube_ldap extends rcube_addressbook
      * @param string $new_name New name to set for this group
      * @param string &$new_gid New group identifier (if changed, otherwise don't set)
      *
-     * @return bool New name on success, false if no data was changed
+     * @return string|false New name on success, false if no data was changed
      */
     public function rename_group($group_id, $new_name, &$new_gid)
     {