diff --git a/plugins/manager/fragments/yform/manager/history.diff.php b/plugins/manager/fragments/yform/manager/history.diff.php
index a63879cd..000dcc92 100644
--- a/plugins/manager/fragments/yform/manager/history.diff.php
+++ b/plugins/manager/fragments/yform/manager/history.diff.php
@@ -13,9 +13,9 @@
 $table = $this->getVar('table', null);
 
 $sql = rex_sql::factory();
-$timestamp = (string) $sql->setQuery(sprintf('SELECT `timestamp` FROM %s WHERE id = %d', rex::getTable('yform_history'), $historyId))->getValue('timestamp');
+$timestamp = $sql->setQuery(sprintf('SELECT `timestamp` FROM %s WHERE id = :id', rex::getTable('yform_history')), [':id' => $historyId])->getValue('timestamp');
 
-$data = $sql->getArray(sprintf('SELECT * FROM %s WHERE history_id = %d', rex::getTable('yform_history_field'), $historyId));
+$data = $sql->getArray(sprintf('SELECT * FROM %s WHERE history_id = :history_id', rex::getTable('yform_history_field')), [':history_id' => $historyId]);
 $data = array_column($data, 'value', 'field');
 
 
@@ -60,17 +60,15 @@
     // count diffs
     if(!$currentDataset->hasValue($field->getName())) {
         $change = 'deleted';
-    } elseif("" . $historyValue != "" . $currentValue) {
+    } elseif("" . $historyValue !== "" . $currentValue) {
         $change = 'changed';
     }
 
     $diffs[$change]['count']++;
 
-    if (is_callable($class, 'getListValue') && !in_array($field->getTypeName(), ['text', 'textarea'])) {
-        /** @var $class rex_yform_value_abstract */
-
+    if (is_callable([$class, 'getListValue']) && !in_array($field->getTypeName(), ['text', 'textarea'], true)) {
         // to ensure correct replacement with list value, ensure datatype by current dataset
-        if(gettype($currentValue) != gettype($historyValue)) {
+        if(gettype($currentValue) !== gettype($historyValue)) {
             settype($historyValue, gettype($currentValue));
         }
 
@@ -105,7 +103,7 @@
     }
 
     // diff values for specific fields
-    if($change == 'changed') {
+    if($change === 'changed') {
         switch($field->getTypeName()) {
             case 'text':
             case 'textarea':
@@ -114,7 +112,7 @@
                 break;
 
             default:
-                if($historyValue != $currentValue) {
+                if($historyValue !== $currentValue) {
                     $historyValue = '<span class="diff">' . $historyValue . '</span>';
                 }
                 break;
@@ -165,14 +163,14 @@
 
 foreach ($diffs as $change => $diff) {
     $content .= '
-        <header class="panel-heading" ' . ($diff['rows'] != '' ? 'data-toggle="collapse" data-target="#collapse-history-table-' . $change . '"' : '') . '>
+        <header class="panel-heading" ' . ($diff['rows'] !== '' ? 'data-toggle="collapse" data-target="#collapse-history-table-' . $change . '"' : '') . '>
             <div class="panel-title"><i class="rex-icon ' . $diff['icon'] . '"></i> ' . rex_i18n::msg('yform_history_diff_headline_' . $change) .
                 ' [' . ($diff['count'] > 0 ? '<b>' : '') . $diff['count'] . ($diff['count'] > 0 ? '</b>' : '') . ']' . '
             </div>
         </header>
-        <div id="collapse-history-table-' . $change . '" ' . ($diff['rows'] != '' ? 'class="panel-collapse collapse ' . ($change == 'changed' ? 'in' : '') . '"' : '') . '>';
+        <div id="collapse-history-table-' . $change . '" ' . ($diff['rows'] !== '' ? 'class="panel-collapse collapse ' . ($change === 'changed' ? 'in' : '') . '"' : '') . '>';
 
-    if($diff['rows'] != '') {
+    if($diff['rows'] !== '') {
         $content .= '       
             <table class="table history-diff-table" data-change-mode="' . $change . '">
                 <thead>
diff --git a/plugins/manager/lib/yform_history_helper.php b/plugins/manager/lib/yform_history_helper.php
index 52f78a4d..8d20d565 100644
--- a/plugins/manager/lib/yform_history_helper.php
+++ b/plugins/manager/lib/yform_history_helper.php
@@ -9,7 +9,7 @@
  */
 class rex_yform_history_helper
 {
-    const FIELD_TYPE_ICONS = [
+    const array FIELD_TYPE_ICONS = [
         'question' => 'question',
 
         'checkbox' => 'square-check',
@@ -40,7 +40,7 @@ class rex_yform_history_helper
         'email' => 'at'
     ];
 
-    const FIELD_TYPE_ICON_WEIGHT_CLASS = 'far';
+    const string FIELD_TYPE_ICON_WEIGHT_CLASS = 'far';
 
     /**
      * detect diffs in 2 strings
@@ -51,13 +51,13 @@ class rex_yform_history_helper
      * @created 17.04.2024
      * @copyright https://github.com/paulgb/simplediff | Paul Butler (paulgb)
      */
-    public static function diffStrings($old, $new):array
+    public static function diffStrings($old, $new): array
     {
         $matrix = array();
-        $maxlen = 0;
+        $maxlen = $omax = $nmax = 0;
 
         foreach ($old as $oindex => $ovalue) {
-            $nkeys = array_keys($new, $ovalue);
+            $nkeys = array_keys($new, $ovalue, true);
 
             foreach ($nkeys as $nindex) {
                 $matrix[$oindex][$nindex] =
@@ -74,14 +74,14 @@ public static function diffStrings($old, $new):array
             }
         }
 
-        if ($maxlen == 0) {
+        if ($maxlen === 0) {
             return array(array('d' => $old, 'i' => $new));
         }
 
         return array_merge(
-            self::diffStrings(array_slice($old, 0, $omax), array_slice($new, 0, $nmax)),
+            rex_yform_history_helper::diffStrings(array_slice($old, 0, $omax), array_slice($new, 0, $nmax)),
             array_slice($new, $nmax, $maxlen),
-            self::diffStrings(array_slice($old, $omax + $maxlen), array_slice($new, $nmax + $maxlen))
+            rex_yform_history_helper::diffStrings(array_slice($old, $omax + $maxlen), array_slice($new, $nmax + $maxlen))
         );
     }
 
@@ -94,20 +94,16 @@ public static function diffStrings($old, $new):array
      * @created 17.04.2024
      * @copyright https://github.com/paulgb/simplediff | Paul Butler (paulgb)
      */
-    public static function diffStringsToHtml($old, $new)
+    public static function diffStringsToHtml($old, $new): string
     {
         $ret = '';
-        $diff = self::diffStrings(preg_split("/[\s]+/", $old), preg_split("/[\s]+/", $new));
+        $diff = rex_yform_history_helper::diffStrings(preg_split("/[\s]+/", $old), preg_split("/[\s]+/", $new));
 
         foreach ($diff as $k) {
-            if (is_array($k)) {
-                $ret .=
-                    (!empty($k['d']) ? "<del>" . implode(' ', $k['d']) . "</del> " : '').
-                    (!empty($k['i']) ? "<ins>" . implode(' ', $k['i']) . "</ins> " : '')
-                ;
-            } else {
-                $ret .= $k . ' ';
-            }
+            $ret .=
+                (isset($k['d']) ? "<del>" . implode(' ', $k['d']) . "</del> " : '').
+                (isset($k['i']) ? "<ins>" . implode(' ', $k['i']) . "</ins> " : '')
+            ;
         }
 
         return $ret;
@@ -126,8 +122,8 @@ public static function diffStringsToHtml($old, $new)
      */
     public static function getFieldTypeIcon(rex_yform_manager_field $field, bool $addPrefix = true, bool $outputHtml = true, bool $addTooltip = true, string $tooltipPlacement = 'top'):string
     {
-        $icon = self::FIELD_TYPE_ICONS[$field->getTypeName()] ?? 'default';
-        $tag = isset(self::FIELD_TYPE_ICONS[$field->getTypeName()]) ? 'i' : 'span';
+        $icon = rex_yform_history_helper::FIELD_TYPE_ICONS[$field->getTypeName()] ?? 'default';
+        $tag = isset(rex_yform_history_helper::FIELD_TYPE_ICONS[$field->getTypeName()]) ? 'i' : 'span';
 
         switch($field->getTypeName()) {
             case 'choice':
@@ -135,9 +131,9 @@ public static function getFieldTypeIcon(rex_yform_manager_field $field, bool $ad
                 $multiple = (bool)(int)$field->getElement('multiple');
 
                 if($expanded && $multiple) {
-                    $icon = self::FIELD_TYPE_ICONS['choice_checkbox'];
+                    $icon = rex_yform_history_helper::FIELD_TYPE_ICONS['choice_checkbox'];
                 } elseif($expanded) {
-                    $icon = self::FIELD_TYPE_ICONS['choice_radio'];
+                    $icon = rex_yform_history_helper::FIELD_TYPE_ICONS['choice_radio'];
                 }
                 break;
         }
@@ -147,7 +143,7 @@ public static function getFieldTypeIcon(rex_yform_manager_field $field, bool $ad
                     ($addTooltip ? ' data-toggle="tooltip" data-placement="' . $tooltipPlacement . '" title="' . rex_i18n::msg('yform_manager_type_name') . ': ' . $field->getTypeName() . '"' : '') .
                     ' class="' : ''
                ).
-               ($icon !== 'default' ? self::FIELD_TYPE_ICON_WEIGHT_CLASS . ' ' : '').($addPrefix ? 'rex-icon ' : '') . 'fa-' . $icon .
+               ($icon !== 'default' ? rex_yform_history_helper::FIELD_TYPE_ICON_WEIGHT_CLASS . ' ' : '').($addPrefix ? 'rex-icon ' : '') . 'fa-' . $icon .
                ($outputHtml ? '"></' . $tag . '>' : '');
     }
 
@@ -164,8 +160,8 @@ public static function getFieldValue(rex_yform_manager_field $field, rex_yform_m
         $class = 'rex_yform_value_' . $field->getTypeName();
         $currentValue = ($dataset->hasValue($field->getName()) ? $dataset->getValue($field->getName()) : '-');
 
-        if (is_callable($class, 'getListValue') && !in_array($field->getTypeName(), ['text','textarea'])) {
-            /** @var $class rex_yform_value_abstract */
+        if (is_callable([$class, 'getListValue']) && !in_array($field->getTypeName(), ['text','textarea'], true)) {
+            /** @var rex_yform_value_abstract $class */
 
             // get (formatted) value for current entry
             if($dataset->hasValue($field->getName())) {
diff --git a/plugins/manager/pages/data_history.php b/plugins/manager/pages/data_history.php
index 0b15e435..75d940c8 100644
--- a/plugins/manager/pages/data_history.php
+++ b/plugins/manager/pages/data_history.php
@@ -214,7 +214,7 @@
 $list->setColumnFormat(
     $revision,
     'custom',
-    static function($a) use (&$rev, &$historyDatasets, &$table, &$sql, &$dataset) {
+    static function($a) use (&$rev, &$historyDatasets, &$table, &$sql) {
         // early column ... store all values for current revision
         $rev = rex::getProperty('YFORM_HISTORY_REVISION', 0);
 
@@ -287,7 +287,7 @@ static function($a) use (&$rev, &$historyDatasets, &$table, &$sql, &$dataset) {
 $list->setColumnFormat(
     $changesCurrent,
     'custom',
-    static function($a) use (&$dataset, $table, $sql, &$historyDatasets, $actionsCell, $normalCell, $changesCurrent) {
+    static function($a) use (&$dataset, $table, &$historyDatasets, $actionsCell, $normalCell, $changesCurrent) {
         $rev = rex::getProperty('YFORM_HISTORY_REVISION', 0) - 1;
 
         $changes = 0;