fix for BIESt #1118

Merge request studip/studip!676

28 files changed, 116 insertions, 101 deletions

diff --git a/lib/classes/ActionMenu.php b/lib/classes/ActionMenu.php
index 92eac8d..511c995 100644
--- a/lib/classes/ActionMenu.php
+++ b/lib/classes/ActionMenu.php
@@ -111,7 +111,8 @@ class ActionMenu
                     'link'       => $url->link,
                     'icon'       => $url->icon,
                     'label'      => $url->label,
-                    'attributes' => $url->attributes
+                    'attributes' => $url->attributes,
+                    'index'      => $index
                 ];
             } else {
                 $action = [
@@ -120,6 +121,7 @@ class ActionMenu
                     'icon'       => $icon,
                     'label'      => $label,
                     'attributes' => $attributes,
+                    'index'      => $index
                 ];
             }
             $index = $index ?: md5($action['link'].json_encode($action['attributes']));
@@ -180,6 +182,7 @@ class ActionMenu
                 'icon'       => $icon,
                 'label'      => $label,
                 'attributes' => $attributes,
+                'index'      => ''
             ];
         }
 
@@ -198,6 +201,7 @@ class ActionMenu
             $this->actions[] = [
                 'type'   => 'multi-person-search',
                 'object' => $mp,
+                'index'  => ''
             ];
         }
 
diff --git a/lib/classes/EventLog.php b/lib/classes/EventLog.php
index b6481d2..7336415 100644
--- a/lib/classes/EventLog.php
+++ b/lib/classes/EventLog.php
@@ -89,6 +89,7 @@ class EventLog
         $filter  = $this->sql_event_filter($action_id, $object_id, $parameters) ?: '1';
         $filter .= " ORDER BY mkdate DESC, event_id DESC LIMIT {$offset}, 50";
         $log_events = LogEvent::findBySQL($filter, $parameters);
+        $events = [];
 
         foreach ($log_events as $log_event) {
             $events[] = [
@@ -113,7 +114,7 @@ class EventLog
         foreach ($actions as $action) {
             $log_actions[$action->getId()] = $action->toArray();
             $log_actions[$action->getId()]['log_count']
-                    = (int) $log_count[$action->getId()];
+                    = (int) ($log_count[$action->getId()] ?? 0);
         }
 
         return $log_actions;
diff --git a/lib/classes/PluginAdministration.php b/lib/classes/PluginAdministration.php
index dc3f3bc..dc8418e 100644
--- a/lib/classes/PluginAdministration.php
+++ b/lib/classes/PluginAdministration.php
@@ -327,6 +327,10 @@ class PluginAdministration
             $plugindir = Config::get()->PLUGINS_PATH . '/' . $plugin['path'];
             $manifest = $plugin_manager->getPluginManifest($plugindir);
 
+            if (!$manifest) {
+                continue;
+            }
+
             if (isset($manifest['updateURL'])) {
                 $repository = new PluginRepository($manifest['updateURL']);
             }
diff --git a/lib/classes/RangeTreeObject.class.php b/lib/classes/RangeTreeObject.class.php
index 95f98b8..c4c5320 100644
--- a/lib/classes/RangeTreeObject.class.php
+++ b/lib/classes/RangeTreeObject.class.php
@@ -7,8 +7,8 @@
 // This file is part of Stud.IP
 // RangeTreeObject.class.php
 // Class to handle items in the "range tree"
-// 
-// Copyright (c) 2002 André Noack <noack@data-quest.de> 
+//
+// Copyright (c) 2002 André Noack <noack@data-quest.de>
 // Suchi & Berg GmbH <info@data-quest.de>
 // +---------------------------------------------------------------------------+
 // This program is free software; you can redistribute it and/or
@@ -28,18 +28,18 @@
 /**
 * base class for items in the "range tree"
 *
-* This class is used for items 
+* This class is used for items
 *
 * @access   public
 * @author   André Noack <noack@data-quest.de>
-* @package  
+* @package
 */
 class RangeTreeObject {
-    
+
     /**
     * item_id in range_tree
     *
-    * 
+    *
     * @access   public
     * @var      string $tree_item_id
     */
@@ -47,7 +47,7 @@ class RangeTreeObject {
     /**
     * References the tree object
     *
-    * 
+    *
     * @access   private
     * @var      object StudipRangeTree $tree
     */
@@ -55,25 +55,25 @@ class RangeTreeObject {
     /**
     * associative array with data from database fields
     *
-    * 
+    *
     * @access   public
     * @var      array $item_data
     */
     var $item_data = null;
-    
+
     /**
     * associative array with mapping for database fields
     *
-    * 
+    *
     * @access   public
     * @var      array $item_data_mapping
     */
     var $item_data_mapping = null;
-    
+
     /**
     * Factory method
     *
-    * 
+    *
     * @access public
     * @static
     * @param    string  $item_id
@@ -84,7 +84,7 @@ class RangeTreeObject {
         $class_name = "RangeTreeObject" . ucfirst($tree->tree_data[$item_id]['studip_object']);
         return new $class_name($item_id);
     }
-    
+
     /**
     * Constructor
     *
@@ -97,11 +97,11 @@ class RangeTreeObject {
         $this->tree_item_id = $item_id;
         $this->item_data = $this->tree->tree_data[$item_id];
     }
-    
+
     /**
     * Returns all tree items which are kids of this object
     *
-    * 
+    *
     * @access public
     * @param    boolean $as_value_list
     * @return   mixed   returns numeric array if param is false, else comma separated string
@@ -109,11 +109,11 @@ class RangeTreeObject {
     function getAllItemKids($as_value_list = false){
         return ($as_value_list) ? $this->getValueList($this->tree->getKidsKids($this->tree_item_id)) : $this->tree->getKidsKids($this->tree_item_id);
     }
-    
+
     /**
     * Returns all tree items which are kids of this object and are "real" Stud.IP objects
     *
-    * 
+    *
     * @access public
     * @param    boolean $as_value_list
     * @return   mixed   returns numeric array if param is false, else comma separated string
@@ -122,11 +122,11 @@ class RangeTreeObject {
         $all_object_kids = array_merge((array)$this->getInstKids(), (array)$this->getFakKids());
         return ($as_value_list) ? $this->getValueList($all_object_kids) : $all_object_kids;
     }
-    
+
     /**
     * Returns all tree items which are kids of this object and are Stud.IP "Einrichtungen"
     *
-    * 
+    *
     * @access public
     * @param    boolean $as_value_list
     * @return   mixed   returns numeric array if param is false, else comma separated string
@@ -141,11 +141,11 @@ class RangeTreeObject {
         }
         return ($as_value_list) ? $this->getValueList($inst_kids) : $inst_kids;
     }
-    
+
     /**
     * Returns all tree items which are kids of this object and are Stud.IP "Fakultaeten"
     *
-    * 
+    *
     * @access public
     * @param    boolean $as_value_list
     * @return   mixed   returns numeric array if param is false, else comma separated string
@@ -160,19 +160,19 @@ class RangeTreeObject {
         }
         return ($as_value_list) ? $this->getValueList($fak_kids) : $fak_kids;
     }
-    
+
     /**
     * Returns array of Stud.IP range_ids of "real" objects
     *
     * This function is a wrapper for the according function in StudipRangeTree
     * @see StudipRangeTree::getAdminRange()
     * @access   public
-    * @return   array   of primary keys from table "institute" 
+    * @return   array   of primary keys from table "institute"
     */
     function getAdminRange(){
         return $this->tree->getAdminRange($this->tree_item_id);
     }
-    
+
     /**
     * Only useful in RangeTreeObjectInst ,all other items are always in the correct branch
     *
@@ -182,24 +182,24 @@ class RangeTreeObject {
     function isInCorrectBranch(){
         return true;
     }
-    
+
     /**
     * Returns tree path of the current object
     *
     * This function is a wrapper for the according function in StudipRangeTree
     * @see StudipRangeTree::getItemPath()
     * @access public
-    * @return   string  
+    * @return   string
     */
     function getItemPath(){
         return $this->tree->getItemPath($this->tree_item_id);
     }
-    
+
     /**
     * extends the $item_data array
     *
     * This function fills the $item_data array with fields from the according database table (is of no use in the base class)
-    * @abstract 
+    * @abstract
     * @access private
     */
     function initItemDetail(){
@@ -220,7 +220,7 @@ class RangeTreeObject {
         }
     return false;
     }
-    
+
     /**
     * fetch categories of this object from database
     *
@@ -238,21 +238,21 @@ class RangeTreeObject {
         }
     return false;
     }
-    
+
     /**
     * getter method for categories of this object
     *
-    * 
+    *
     * @access public
     * @return   object DbSnapshot
     */
     function &getCategories(){
-        if (!is_object($this->item_data['categories'])){
+        if (empty($this->item_data['categories']) || !is_object($this->item_data['categories'])){
             $this->fetchCategories();
         }
         return $this->item_data['categories'];
     }
-    
+
     function fetchNumStaff(){
         $view = DbView::getView('range_tree');
         if (!($view->params[0] = $this->item_data['studip_object_id']))
@@ -264,15 +264,15 @@ class RangeTreeObject {
         }
         return false;
     }
-    
+
     function getNumStaff(){
         if(!isset($this->item_data['num_staff'])){
             $this->fetchNumStaff();
         }
         return $this->item_data['num_staff'];
     }
-    
-    
+
+
     /**
     * transform numerical array into a comma separated string
     *
@@ -281,12 +281,12 @@ class RangeTreeObject {
     * @param    array   $list
     * @return   string
     */
-    
+
     function getValueList($list){
         $value_list = false;
-        if (count($list) == 1) 
+        if (count($list) == 1)
             $value_list = "'$list[0]'";
-        else 
+        else
             $value_list = "'".join("','",$list)."'";
         return $value_list;
     }
diff --git a/lib/classes/SemClass.class.php b/lib/classes/SemClass.class.php
index 5ab5a2d..dbbbcd7 100644
--- a/lib/classes/SemClass.class.php
+++ b/lib/classes/SemClass.class.php
@@ -305,7 +305,7 @@ class SemClass implements ArrayAccess
      */
     public function isModuleActivated($modulename)
     {
-        return !$this->data['modules'][$modulename]
+        return empty($this->data['modules'][$modulename])
             ||  $this->data['modules'][$modulename]['activated'];
     }
 
@@ -316,7 +316,7 @@ class SemClass implements ArrayAccess
      */
     public function isModuleAllowed($modulename)
     {
-        return !$this->data['modules'][$modulename]
+        return empty($this->data['modules'][$modulename])
             || !$this->data['modules'][$modulename]['sticky']
             ||  $this->data['modules'][$modulename]['activated'];
     }
diff --git a/lib/classes/StudipForm.class.php b/lib/classes/StudipForm.class.php
index 88c36fe..024e2e3 100644
--- a/lib/classes/StudipForm.class.php
+++ b/lib/classes/StudipForm.class.php
@@ -182,7 +182,7 @@ class StudipForm {
             $attributes['required'] = 'required';
         }
 
-        if (!isset($attributes['id'])) {
+        if (empty($attributes['id'])) {
             $attributes['id'] = $this->form_name . '_' . $name;
         }
 
@@ -282,7 +282,7 @@ class StudipForm {
 
     function getFormFieldSelect($name, $attributes, $default){
         $ret = "\n<select name=\"{$this->form_name}_{$name}";
-        if (!empty($this->form_fields[$name]['multiple'])){
+        if (!empty($this->form_fields[$name]['multiple'])) {
             $ret .= "[]\" multiple ";
         } else {
             $ret .= "\" ";
@@ -292,9 +292,9 @@ class StudipForm {
         if ($default === false){
             $default = $this->form_fields[$name]['default_value'];
         }
-        if (!empty($this->form_fields[$name]['options']) && is_array($this->form_fields[$name]['options'])){
+        if (!empty($this->form_fields[$name]['options']) && is_array($this->form_fields[$name]['options'])) {
             $options = $this->form_fields[$name]['options'];
-        } else if ($this->form_fields[$name]['options_callback']){
+        } else if (!empty($this->form_fields[$name]['options_callback'])) {
             $options = call_user_func($this->form_fields[$name]['options_callback'],$this,$name);
         }
         for ($i = 0; $i < count($options); ++$i){
diff --git a/lib/classes/StudipRangeTree.class.php b/lib/classes/StudipRangeTree.class.php
index 291d443..36f7314 100644
--- a/lib/classes/StudipRangeTree.class.php
+++ b/lib/classes/StudipRangeTree.class.php
@@ -61,7 +61,7 @@ class StudipRangeTree extends TreeAbstract
         if (isset($args['sem_status']) ){
             $this->sem_status = array_map('intval', $args['sem_status']);
         }
-        $this->visible_only = (int)$args['visible_only'];
+        $this->visible_only = (int)($args['visible_only'] ?? 0);
         parent::__construct(); //calling the baseclass constructor
         $this->sem_dates = Semester::findAllVisible();
     }
diff --git a/lib/classes/StudipRangeTreeViewAdmin.class.php b/lib/classes/StudipRangeTreeViewAdmin.class.php
index 1bde371..6c5f349 100644
--- a/lib/classes/StudipRangeTreeViewAdmin.class.php
+++ b/lib/classes/StudipRangeTreeViewAdmin.class.php
@@ -576,7 +576,7 @@ class StudipRangeTreeViewAdmin extends TreeView{
             return $content;
         }
         $range_object = RangeTreeObject::GetInstance($item_id);
-        $name = ($range_object->item_data['type']) ? $range_object->item_data['type'] . ": " : "";
+        $name = !empty($range_object->item_data['type']) ? $range_object->item_data['type'] . ": " : "";
         $name .= $range_object->item_data['name'];
         $content .= "\n<tr><td class=\"table_header_bold\" align=\"left\" style=\"font-size:10pt\">" . htmlReady($name) ." </td></tr>";
         if (is_array($range_object->item_data_mapping)){
@@ -728,7 +728,7 @@ class StudipRangeTreeViewAdmin extends TreeView{
         </div>
 
         <?
-        $content .= ob_get_clean();
+        $content = ob_get_clean();
         return $content;
     }
 
@@ -787,7 +787,7 @@ class StudipRangeTreeViewAdmin extends TreeView{
             </footer>
         </form>
 
-        <? $content .= ob_get_clean() . '</td></tr>';
+        <? $content = ob_get_clean() . '</td></tr>';
 
         return $content;
     }
@@ -795,7 +795,7 @@ class StudipRangeTreeViewAdmin extends TreeView{
     function getItemMessage($item_id, $colspan = 1)
     {
         $content = "";
-        if ($this->msg[$item_id]){
+        if (!empty($this->msg[$item_id])) {
             $msg = explode("§", $this->msg[$item_id]);
             $pics = [
                 'error' => Icon::create('decline', 'attention'),
diff --git a/lib/classes/StudipSemSearchHelper.class.php b/lib/classes/StudipSemSearchHelper.class.php
index e87da1b..ea7aa9c 100644
--- a/lib/classes/StudipSemSearchHelper.class.php
+++ b/lib/classes/StudipSemSearchHelper.class.php
@@ -103,7 +103,7 @@ class StudipSemSearchHelper {
         if (isset($this->params['type']) && $this->params['type'] != 'all'){
             $sem_types = [$this->params['type']];
         }
-        if ($sem_types) {
+        if (!empty($sem_types) && is_array($sem_types)) {
             $clause = " AND c.status IN('" . join("','",$sem_types) . "') " . $clause;
         }
 
diff --git a/lib/classes/StudipSemTree.class.php b/lib/classes/StudipSemTree.class.php
index 82fd37c..203bec1 100644
--- a/lib/classes/StudipSemTree.class.php
+++ b/lib/classes/StudipSemTree.class.php
@@ -110,7 +110,7 @@ class StudipSemTree extends TreeAbstract
 
     public function isHiddenItem($item_id)
     {
-        return (bool) $GLOBALS['SEM_TREE_TYPES'][$this->getValue($item_id, 'type')]['hidden'];
+        return !empty($GLOBALS['SEM_TREE_TYPES'][$this->getValue($item_id, 'type')]['hidden']);
     }
 
     public function getSemIds($item_id,$ids_from_kids = false)
@@ -173,11 +173,11 @@ class StudipSemTree extends TreeAbstract
 
     public function getNumEntries($item_id, $num_entries_from_kids = false)
     {
-        if (!$this->tree_data[$item_id]) {
+        if (empty($this->tree_data[$item_id])) {
             return false;
         }
 
-        if (!$this->entries_init_done) {
+        if (empty($this->entries_init_done)) {
             $this->initEntries();
         }
 
diff --git a/lib/classes/StudipSemTreeViewAdmin.class.php b/lib/classes/StudipSemTreeViewAdmin.class.php
index 8644fef..c615f98 100644
--- a/lib/classes/StudipSemTreeViewAdmin.class.php
+++ b/lib/classes/StudipSemTreeViewAdmin.class.php
@@ -105,6 +105,7 @@ class StudipSemTreeViewAdmin extends TreeView
     }
 
     function parseCommand(){
+        $this->mode = '';
         if (Request::quoted('mode'))
         $this->mode = Request::quoted('mode');
         if (Request::option('cmd')){
@@ -483,7 +484,7 @@ class StudipSemTreeViewAdmin extends TreeView
         $head = $this->getItemHeadFrontPic($item_id);
         $head .= "\n<td  class=\"printhead\" nowrap  align=\"left\" valign=\"bottom\">";
         if ($this->tree->hasKids($item_id)){
-            $head .= Icon::create('folder-full', 'clickable', ['title' => $this->open_ranges[$item_id]?_('Alle Unterelemente schliessen'):_('Alle Unterelemente öffnen')])->asImg(16, ['class' => 'text-top']);
+            $head .= Icon::create('folder-full', Icon::ROLE_CLICKABLE, ['title' => !empty($this->open_ranges[$item_id]) ? _('Alle Unterelemente schliessen') : _('Alle Unterelemente öffnen')])->asImg(['class' => 'text-top']);
         } else {
             $head .= Icon::create('folder-empty', 'clickable', ['title' => _('Dieses Element hat keine Unterelemente')])->asImg();
         }
@@ -491,18 +492,18 @@ class StudipSemTreeViewAdmin extends TreeView
     }
 
     function getItemContent($item_id){
-        if ($item_id == $this->edit_item_id ) return $this->getEditItemContent();
-        if(!$GLOBALS['SEM_TREE_TYPES'][$this->tree->getValue($item_id, 'type')]['editable']){
+        if (!empty($this->edit_item_id) && ($item_id == $this->edit_item_id)) return $this->getEditItemContent();
+        if(empty($GLOBALS['SEM_TREE_TYPES'][$this->tree->getValue($item_id, 'type')]['editable'])){
             $is_not_editable = true;
             $this->msg[$item_id] = "info§" . sprintf(_("Der Typ dieses Elementes verbietet eine Bearbeitung."));
         }
-        if ($item_id == $this->move_item_id){
+        if (!empty($this->move_item_id) && ($item_id == $this->move_item_id)) {
             $this->msg[$item_id] = "info§" . sprintf(_("Dieses Element wurde zum Verschieben / Kopieren markiert. Bitte wählen Sie ein Einfügesymbol %s aus, um das Element zu verschieben / kopieren."), Icon::create('arr_2right', 'sort', ['title' => "Einfügesymbol"])->asImg(16, ["alt" => "Einfügesymbol"]));
         }
         $content = "\n<table width=\"90%\" cellpadding=\"2\" cellspacing=\"2\" align=\"center\" style=\"font-size:10pt;\">";
         $content .= $this->getItemMessage($item_id);
         $content .= "\n<tr><td style=\"font-size:10pt;\">";
-        if(!$is_not_editable){
+        if (empty($is_not_editable)) {
             if ($this->isItemAdmin($item_id) ){
                 $content .= LinkButton::create(_('Neues Objekt'),
                         URLHelper::getURL($this->getSelf('cmd=NewItem&item_id='.$item_id)),
@@ -520,7 +521,7 @@ class StudipSemTreeViewAdmin extends TreeView
                         URLHelper::getURL($this->getSelf('cmd=AssertDeleteItem&item_id=' . $item_id)),
                         ['title' => _('Dieses Element löschen')]) . '&nbsp;';
 
-                if ($this->move_item_id == $item_id && ($this->mode == "MoveItem" || $this->mode == "CopyItem")){
+                if (!empty($this->move_item_id) && ($this->move_item_id == $item_id) && ($this->mode == "MoveItem" || $this->mode == "CopyItem")){
                     $content .= LinkButton::create(_('Abbrechen'),
                             URLHelper::getURL($this->getSelf('cmd=Cancel&item_id=' . $item_id)),
                             ['title' => _('Verschieben / Kopieren abbrechen')]) . '&nbsp;';
@@ -561,7 +562,7 @@ class StudipSemTreeViewAdmin extends TreeView
             $content .= formatReady($this->tree->tree_data[$item_id]['info']) . "</td></tr>";
         }
         $content .= "<tr><td style=\"font-size:10pt;\"colspan=\"3\">&nbsp;</td></tr>";
-        if ($this->tree->getNumEntries($item_id) - $this->tree->tree_data[$item_id]['lonely_sem']){
+        if (!empty($this->tree->tree_data[$item_id]['lonely_sem']) && ($this->tree->getNumEntries($item_id) - $this->tree->tree_data[$item_id]['lonely_sem'])) {
             $content .= "<tr><td class=\"table_row_even\" style=\"font-size:10pt;\" align=\"left\" colspan=\"3\"><b>" . _("Einträge auf dieser Ebene:");
             $content .= "</b>\n</td></tr>";
             $entries = $this->tree->getSemData($item_id);
@@ -569,7 +570,7 @@ class StudipSemTreeViewAdmin extends TreeView
         } else {
             $content .= "\n<tr><td class=\"table_row_even\" style=\"font-size:10pt;\" colspan=\"3\">" . _("Keine Einträge auf dieser Ebene vorhanden!") . "</td></tr>";
         }
-        if ($this->tree->tree_data[$item_id]['lonely_sem']){
+        if (!empty($this->tree->tree_data[$item_id]['lonely_sem'])) {
             $content .= "<tr><td class=\"table_row_even\" align=\"left\" style=\"font-size:10pt;\" colspan=\"3\"><b>" . _("Nicht zugeordnete Veranstaltungen auf dieser Ebene:");
             $content .= "</b>\n</td></tr>";
             $entries = $this->tree->getLonelySemData($item_id);
@@ -775,7 +776,7 @@ class StudipSemTreeViewAdmin extends TreeView
         if ($item_id != "root"){
             $head .= " (" . $this->tree->getNumEntries($item_id,true) . ") " ;
         }
-        if ($item_id != $this->start_item_id && $this->isParentAdmin($item_id) && $item_id != $this->edit_item_id){
+        if ($item_id != $this->start_item_id && $this->isParentAdmin($item_id) && !empty($this->edit_item_id) && ($item_id != $this->edit_item_id)){
             $head .= "</td><td nowrap align=\"right\" valign=\"bottom\" class=\"printhead\">";
             if (!$this->tree->isFirstKid($item_id)){
                 $head .= "<a href=\"". URLHelper::getLink($this->getSelf("cmd=OrderItem&direction=up&item_id=$item_id")) .
@@ -794,7 +795,7 @@ class StudipSemTreeViewAdmin extends TreeView
 
     function getItemMessage($item_id,$colspan = 1){
         $content = "";
-        if ($this->msg[$item_id]){
+        if (!empty($this->msg[$item_id])) {
             $msg = explode("§",$this->msg[$item_id]);
             $pics = [
                 'error' => Icon::create('decline', 'attention'),
diff --git a/lib/classes/TreeView.class.php b/lib/classes/TreeView.class.php
index b2d8f5b..243a9b9 100644
--- a/lib/classes/TreeView.class.php
+++ b/lib/classes/TreeView.class.php
@@ -168,7 +168,7 @@ class TreeView {
 
         $toggle_item = Request::option('close_item') ?: Request::option('open_item');
         if ($toggle_item){
-            if ($this->open_items[$toggle_item]) {
+            if (!empty($this->open_items[$toggle_item])) {
                 unset($this->open_items[$toggle_item]);
             } else {
                 $this->openItem($toggle_item);
@@ -216,7 +216,7 @@ class TreeView {
     for ($j = 0; $j < $num_items; ++$j){
         $this->printLevelOutput($items[$j]);
         $this->printItemOutput($items[$j]);
-        if ($this->tree->hasKids($items[$j]) && $this->open_ranges[$items[$j]]) {
+        if ($this->tree->hasKids($items[$j]) && !empty($this->open_ranges[$items[$j]])) {
             $this->showTree($this->tree->tree_childs[$items[$j]]);
         }
     }
@@ -276,7 +276,7 @@ class TreeView {
         echo "\n</td><td class=\"printhead\" align=\"left\" width=\"99%\" nowrap valign=\"bottom\">";
         echo $this->getItemHead($item_id);
         echo "</td></tr></table>";
-        if ($this->open_items[$item_id]) {
+        if (!empty($this->open_items[$item_id])) {
             $this->printItemDetails($item_id);
         }
         return;
@@ -318,7 +318,7 @@ class TreeView {
                 else
                     $level_output = "<td class=\"blank\" background=\"" . Assets::image_path('forumstrich.gif') . "\">"
                                   . Assets::img('forumleer.gif', ['size' => '10@20'])
-                                  . "</td>" . $level_output; //vertical line
+                                  . "</td>" . ($level_output ?? ''); //vertical line
             }
         }
         //$level_output = "<td class=\"blank\" background=\"".$GLOBALS['ASSETS_URL']."images/forumleer.gif\" ><img src=\"".$GLOBALS['ASSETS_URL']."images/forumleer.gif\" width=\"20\" height=\"20\" border=\"0\" ></td>" . $level_output;
@@ -342,9 +342,11 @@ class TreeView {
         $head .= "\n<td  class=\"printhead\" nowrap align=\"left\" valign=\"bottom\">";
         if ($this->tree->hasKids($item_id)){
             $head .= "<a href=\"";
-            $head .= ($this->open_ranges[$item_id]) ? URLHelper::getLink($this->getSelf("close_range={$item_id}")) : URLHelper::getLink($this->getSelf("open_range={$item_id}"));
+            $head .= !empty($this->open_ranges[$item_id])
+                ? URLHelper::getLink($this->getSelf("close_range={$item_id}"))
+                : URLHelper::getLink($this->getSelf("open_range={$item_id}"));
             $head .= "\">";
-            $head .= Icon::create('folder-full', 'clickable', ['title' => $this->open_ranges[$item_id]?_('Alle Unterelemente schließen'):_('Alle Unterelemente öffnen')])->asImg(16, ['class' => 'text-top']);
+            $head .= Icon::create('folder-full', 'clickable', ['title' => !empty($this->open_ranges[$item_id]) ? _('Alle Unterelemente schließen') : _('Alle Unterelemente öffnen')])->asImg(16, ['class' => 'text-top']);
             $head .= "</a>";
         } else {
             $head .= Icon::create('folder-empty', 'clickable', ['title' => _('Dieses Element hat keine Unterelemente')])->asImg();
@@ -362,9 +364,10 @@ class TreeView {
             $head = "<td class=\"printhead\" nowrap align=\"left\" valign=\"bottom\">";
         }
         $head .= "<a href=\"";
-        $head .= ($this->open_items[$item_id])? URLHelper::getLink($this->getSelf("close_item={$item_id}")) . "\"" . tooltip(_("Dieses Element schließen"),true) . ">"
-                                            : URLHelper::getLink($this->getSelf("open_item={$item_id}")) . "\"" . tooltip(_("Dieses Element öffnen"),true) . ">";
-        $head .= Assets::img($this->open_items[$item_id] ? $this->pic_open : $this->pic_close);
+        $head .= !empty($this->open_items[$item_id])
+            ? URLHelper::getLink($this->getSelf("close_item={$item_id}")) . "\"" . tooltip(_("Dieses Element schließen"),true) . ">"
+            : URLHelper::getLink($this->getSelf("open_item={$item_id}")) . "\"" . tooltip(_("Dieses Element öffnen"),true) . ">";
+        $head .= Assets::img(!empty($this->open_items[$item_id]) ? $this->pic_open : $this->pic_close);
         #$head .= (!$this->open_items[$item_id]) ? "<img  src=\"".$GLOBALS['ASSETS_URL']."images/forumleer.gif\" width=\"5\" border=\"0\">" : "";
         $head .= "</a>";
         $head .= '</td>';
@@ -381,10 +384,11 @@ class TreeView {
     function getItemHead($item_id){
         $head = "";
         $head .= "&nbsp;<a class=\"tree\" href=\"";
-        $head .= ($this->open_items[$item_id])? URLHelper::getLink($this->getSelf("close_item={$item_id}")) . "\"" . tooltip(_("Dieses Element schließen"),true) . "><b>"
-                                            : URLHelper::getLink($this->getSelf("open_item={$item_id}")) . "\"" . tooltip(_("Dieses Element öffnen"),true) . ">";
+        $head .= !empty($this->open_items[$item_id])
+            ? URLHelper::getLink($this->getSelf("close_item={$item_id}")) . "\"" . tooltip(_("Dieses Element schließen"),true) . "><b>"
+            : URLHelper::getLink($this->getSelf("open_item={$item_id}")) . "\"" . tooltip(_("Dieses Element öffnen"),true) . ">";
         $head .= htmlReady(my_substr($this->tree->tree_data[$item_id]['name'],0,$this->max_cols));
-        $head .= ($this->open_items[$item_id]) ? "</b></a>" : "</a>";
+        $head .= (!empty($this->open_items[$item_id])) ? "</b></a>" : "</a>";
         return $head;
     }
 
diff --git a/lib/classes/URLHelper.php b/lib/classes/URLHelper.php
index ae83022..732ce99 100644
--- a/lib/classes/URLHelper.php
+++ b/lib/classes/URLHelper.php
@@ -69,7 +69,7 @@ class URLHelper
 
         if ($url[0] === '/') {
             preg_match('%^[a-z]+://[\w:.-]+%', $base_url, $host);
-            $base_url = isset($host) ? $host[0] : '';
+            $base_url = $host[0] ?? '';
         }
 
         return $base_url.$url;
diff --git a/lib/classes/restapi/Router.php b/lib/classes/restapi/Router.php
index a66463e..d6a331c 100644
--- a/lib/classes/restapi/Router.php
+++ b/lib/classes/restapi/Router.php
@@ -322,8 +322,8 @@ class Router
                 }
                 if ($describe) {
                     $result[$uri][$method] = [
-                        'description' => $this->descriptions[$uri][$method] ?: null,
-                        'source'      => $route['source'] ?: 'unknown',
+                        'description' => $this->descriptions[$uri][$method] ?? null,
+                        'source'      => $route['source'] ?? 'unknown',
                     ];
                 } else {
                     $result[$uri][] = $method;
diff --git a/lib/classes/searchtypes/RangeSearch.class.php b/lib/classes/searchtypes/RangeSearch.class.php
index ee7f969..b9c83ae 100644
--- a/lib/classes/searchtypes/RangeSearch.class.php
+++ b/lib/classes/searchtypes/RangeSearch.class.php
@@ -10,6 +10,7 @@ class RangeSearch extends SQLSearch
 
     public function __construct()
     {
+        $this->avatarLike = $this->search = '';
         $this->sql = $this->getSQL();
     }
 
diff --git a/lib/extern/admin_extern.inc.php b/lib/extern/admin_extern.inc.php
index 0b6affe..fd436c4 100644
--- a/lib/extern/admin_extern.inc.php
+++ b/lib/extern/admin_extern.inc.php
@@ -315,7 +315,7 @@ else {
 }
 
 
-if (!$have_config) {
+if (empty($have_config)) {
     echo "<blockquote>\n";
     echo _("Es wurden noch keine Konfigurationen angelegt.");
     echo "</blockquote>";
diff --git a/lib/extern/lib/ExternConfig.class.php b/lib/extern/lib/ExternConfig.class.php
index 226dbe7..4c34625 100644
--- a/lib/extern/lib/ExternConfig.class.php
+++ b/lib/extern/lib/ExternConfig.class.php
@@ -121,7 +121,7 @@ class ExternConfig
     {
         foreach ($config as $element_name => $element) {
             if (is_array($element)) foreach ($element as $attribute => $value) {
-                if ((string)$value[0] == '|') {
+                if (!empty($value[0]) && (string)$value[0] == '|') {
                     $new_config[$element_name][$attribute] = explode('|', mb_substr($value, 1));
                 } else {
                     $new_config[$element_name][$attribute] = $value;
diff --git a/lib/extern/lib/ExternConfigDb.class.php b/lib/extern/lib/ExternConfigDb.class.php
index 1f23a86..c1ab29b 100644
--- a/lib/extern/lib/ExternConfigDb.class.php
+++ b/lib/extern/lib/ExternConfigDb.class.php
@@ -77,7 +77,7 @@ class ExternConfigDb extends ExternConfig
         if (!parent::insertConfiguration()) {
             return false;
         }
-         $serialized_config = json_encode($this->config);
+         $serialized_config = json_encode($this->config ?? null);
          $time = time();
          $query = "INSERT INTO extern_config VALUES (?, ?, ?, ?, 0, ?, ?, ?)";
          $statement = DBManager::get()->prepare($query);
diff --git a/lib/extern/views/extern_edit_module.inc.php b/lib/extern/views/extern_edit_module.inc.php
index 8c4bac4..21c5c88 100644
--- a/lib/extern/views/extern_edit_module.inc.php
+++ b/lib/extern/views/extern_edit_module.inc.php
@@ -145,7 +145,7 @@ if (Request::option('com') == 'store') {
 }
 
 
-if (!$edit_open[$edit]) {
+if (empty($edit_open[$edit])) {
     echo  LinkButton::create("<< " . _("Zurück"), URLHelper::getURL('?list=TRUE'));;
 }
 
diff --git a/lib/functions.php b/lib/functions.php
index 9986104..a86a9c4 100644
--- a/lib/functions.php
+++ b/lib/functions.php
@@ -1420,7 +1420,7 @@ function get_route($route = '')
     if (mb_strpos($route, 'plugins.php/') !== false) {
         $trails = explode('plugins.php/', $route);
         $pieces = explode('/', $trails[1]);
-        $route = 'plugins.php/' . $pieces[0] . ($pieces[1] ? '/' . $pieces[1] : '') . ($pieces[2] ? '/' . $pieces[2] : '');
+        $route = 'plugins.php/' . $pieces[0] . (!empty($pieces[1]) ? '/' . $pieces[1] : '') . (!empty($pieces[2]) ? '/' . $pieces[2] : '');
     } elseif (mb_strpos($route, 'dispatch.php/') !== false) {
         $trails = explode('dispatch.php/', $route);
         $dispatcher = new StudipDispatcher();
diff --git a/lib/models/LogEvent.php b/lib/models/LogEvent.php
index 38fdd72..2e83590 100644
--- a/lib/models/LogEvent.php
+++ b/lib/models/LogEvent.php
@@ -279,7 +279,7 @@ class LogEvent extends SimpleORMap implements PrivacyObject
     protected function formatSemester($field) {
         $all_semester = Semester::findAllVisible(false);
         foreach ($all_semester as $val) {
-            if ($val['beginn'] == $this->$field) {
+            if (!empty($val['beginn']) && ($val['beginn'] == $this->$field)) {
                 return '<em>' . $val['name'] . '</em>';
             }
         }
diff --git a/lib/models/OERHost.php b/lib/models/OERHost.php
index 7cb2ba5..1c7c01e 100644
--- a/lib/models/OERHost.php
+++ b/lib/models/OERHost.php
@@ -15,7 +15,7 @@ class OERHost extends OERIdentity
     {
         $host = self::findOneBySQL("`private_key` IS NOT NULL AND `sorm_class` = 'OERHost' LIMIT 1");
         if ($host) {
-            $host['url'] = $GLOBALS['oer_PREFERRED_URI'] ?: $GLOBALS['ABSOLUTE_URI_STUDIP']."dispatch.php/oer/endpoints/";
+            $host['url'] = $GLOBALS['oer_PREFERRED_URI'] ?? $GLOBALS['ABSOLUTE_URI_STUDIP']."dispatch.php/oer/endpoints/";
             if ($host->isFieldDirty("url")) {
                 $host->store();
             }
@@ -23,7 +23,7 @@ class OERHost extends OERIdentity
         } else {
             $host = new self();
             $host['name'] = Config::get()->UNI_NAME_CLEAN;
-            $host['url'] = $GLOBALS['oer_PREFERRED_URI'] ?: $GLOBALS['ABSOLUTE_URI_STUDIP']."dispatch.php/oer/endpoints/";
+            $host['url'] = $GLOBALS['oer_PREFERRED_URI'] ?? $GLOBALS['ABSOLUTE_URI_STUDIP']."dispatch.php/oer/endpoints/";
             $host['last_updated'] = time();
             $host->store();
             return $host;
diff --git a/lib/models/SimpleCollection.class.php b/lib/models/SimpleCollection.class.php
index 588de1b..26439b2 100644
--- a/lib/models/SimpleCollection.class.php
+++ b/lib/models/SimpleCollection.class.php
@@ -684,9 +684,9 @@ class SimpleCollection extends StudipArrayObject
 
         $func = function ($d1, $d2) use ($sorter, $sort_func, $sort_locale) {
             do {
-                $field = current($sorter);
-                $dir = $field[1] ?? '';
-                $field = $field[0] ?? '';
+                $current_sorter = current($sorter);
+                $field = $current_sorter[0];
+                $dir = $current_sorter[1] ?? '';
                 if (!$sort_locale) {
                     $value1 = $d1[$field];
                     $value2 = $d2[$field];
diff --git a/lib/models/SimpleORMap.class.php b/lib/models/SimpleORMap.class.php
index 5fed34a..bc670d8 100644
--- a/lib/models/SimpleORMap.class.php
+++ b/lib/models/SimpleORMap.class.php
@@ -1094,14 +1094,14 @@ class SimpleORMap implements ArrayAccess, Countable, IteratorAggregate
         }
         if ($type === 'has_and_belongs_to_many') {
             $thru_table = $options['thru_table'];
-            if (!$options['thru_key']) {
+            if (empty($options['thru_key'])) {
                 $options['thru_key'] = $this->pk()[0];
             }
             if (empty($options['thru_assoc_key']) || empty($options['assoc_foreign_key'])) {
                 $class = $options['class_name'];
                 $record = new $class();
                 $meta = $record->getTableMetadata();
-                if (!$options['thru_assoc_key'] ) {
+                if (empty($options['thru_assoc_key'])) {
                     $options['thru_assoc_key'] = $meta['pk'][0];
                 }
                 if (empty($options['assoc_foreign_key'])) {
diff --git a/lib/models/User.class.php b/lib/models/User.class.php
index 7ce868b..7eb1321 100644
--- a/lib/models/User.class.php
+++ b/lib/models/User.class.php
@@ -365,7 +365,7 @@ class User extends AuthUserMd5 implements Range, PrivacyObject
         }
 
         //locked user
-        if ((int)$attributes['locked'] == 1) {
+        if (!empty($attributes['locked'])) {
             $where[] = "au.`locked` = 1";
         }
 
diff --git a/lib/plugins/engine/PluginManager.class.php b/lib/plugins/engine/PluginManager.class.php
index 7193f31..7ced174 100644
--- a/lib/plugins/engine/PluginManager.class.php
+++ b/lib/plugins/engine/PluginManager.class.php
@@ -657,9 +657,9 @@ class PluginManager
         }
 
         foreach ($manifest as $line) {
-            list($key, $value) = explode('=', $line);
-            $key = trim($key);
-            $value = trim($value);
+            $key_and_value = explode('=', $line);
+            $key = trim($key_and_value[0]);
+            $value = trim($key_and_value[1] ?? '');
 
             // skip empty lines and comments
             if ($key === '' || $key[0] === '#') {
diff --git a/lib/plugins/engine/PluginRepository.class.php b/lib/plugins/engine/PluginRepository.class.php
index ef09a6c..14415f4 100644
--- a/lib/plugins/engine/PluginRepository.class.php
+++ b/lib/plugins/engine/PluginRepository.class.php
@@ -116,7 +116,7 @@ class PluginRepository
      */
     protected function registerPlugin($name, $meta_data)
     {
-        $old_data = $this->plugins[$name];
+        $old_data = $this->plugins[$name] ?? null;
 
         if (!isset($old_data) ||
             version_compare($meta_data['version'], $old_data['version']) > 0) {
@@ -132,7 +132,7 @@ class PluginRepository
      */
     public function getPlugin($name)
     {
-        return $this->plugins[$name];
+        return $this->plugins[$name] ?? null;
     }
 
     /**
diff --git a/lib/visual.inc.php b/lib/visual.inc.php
index 303987d..9cf78c3 100644
--- a/lib/visual.inc.php
+++ b/lib/visual.inc.php
@@ -679,7 +679,7 @@ function TransformInternalLinks($str){
         }
         $str = $GLOBALS['ABSOLUTE_URI_STUDIP'] . $str;
     }
-    if (is_array($GLOBALS['STUDIP_DOMAINS']) && count($GLOBALS['STUDIP_DOMAINS']) > 1) {
+    if (!empty($GLOBALS['STUDIP_DOMAINS']) && count($GLOBALS['STUDIP_DOMAINS']) > 1) {
         if (!isset($GLOBALS['TransformInternalLinks_domainData'])){
             $domain_data['domains'] = '';
             foreach ($GLOBALS['STUDIP_DOMAINS'] as $studip_domain) $domain_data['domains'] .= '|' . preg_quote($studip_domain);