diff --git a/includes/controller/shift_entries_controller.php b/includes/controller/shift_entries_controller.php
index c2851c7c..cb2d9bee 100644
--- a/includes/controller/shift_entries_controller.php
+++ b/includes/controller/shift_entries_controller.php
@@ -12,7 +12,7 @@ function shift_entry_add_controller()
     global $privileges, $user;
 
     $shift_id = 0;
-    if (isset($_REQUEST['shift_id']) && preg_match('/^[0-9]*$/', $_REQUEST['shift_id'])) {
+    if (isset($_REQUEST['shift_id']) && preg_match('/^\d*$/', $_REQUEST['shift_id'])) {
         $shift_id = $_REQUEST['shift_id'];
     } else {
         redirect(page_link_to('user_shifts'));
@@ -32,7 +32,7 @@ function shift_entry_add_controller()
     }
 
     $type_id = 0;
-    if (isset($_REQUEST['type_id']) && preg_match('/^[0-9]*$/', $_REQUEST['type_id'])) {
+    if (isset($_REQUEST['type_id']) && preg_match('/^\d*$/', $_REQUEST['type_id'])) {
         $type_id = $_REQUEST['type_id'];
     } else {
         redirect(page_link_to('user_shifts'));
@@ -64,7 +64,7 @@ function shift_entry_add_controller()
 
     if (
         isset($_REQUEST['user_id'])
-        && preg_match('/^[0-9]*$/', $_REQUEST['user_id'])
+        && preg_match('/^\d*$/', $_REQUEST['user_id'])
         && (
             in_array('user_shifts_admin', $privileges)
             || in_array('shiftentry_edit_angeltype_supporter', $privileges)
diff --git a/includes/controller/shifts_controller.php b/includes/controller/shifts_controller.php
index 989f1a69..71459a10 100644
--- a/includes/controller/shifts_controller.php
+++ b/includes/controller/shifts_controller.php
@@ -78,7 +78,7 @@ function shift_edit_controller()
         $title = strip_request_item('title');
 
         // Auswahl der sichtbaren Locations für die Schichten
-        if (isset($_REQUEST['rid']) && preg_match('/^[0-9]+$/', $_REQUEST['rid']) && isset($room[$_REQUEST['rid']])) {
+        if (isset($_REQUEST['rid']) && preg_match('/^\d+$/', $_REQUEST['rid']) && isset($room[$_REQUEST['rid']])) {
             $rid = $_REQUEST['rid'];
         } else {
             $valid = false;
@@ -192,7 +192,7 @@ function shift_delete_controller()
     }
 
     // Schicht komplett löschen (nur für admins/user mit user_shifts_admin privileg)
-    if (!isset($_REQUEST['delete_shift']) || !preg_match('/^[0-9]*$/', $_REQUEST['delete_shift'])) {
+    if (!isset($_REQUEST['delete_shift']) || !preg_match('/^\d*$/', $_REQUEST['delete_shift'])) {
         redirect(page_link_to('user_shifts'));
     }
     $shift_id = $_REQUEST['delete_shift'];
@@ -360,7 +360,7 @@ function shifts_json_export_controller()
 {
     global $user;
 
-    if (!isset($_REQUEST['key']) || !preg_match('/^[0-9a-f]{32}$/', $_REQUEST['key'])) {
+    if (!isset($_REQUEST['key']) || !preg_match('/^[\da-f]{32}$/', $_REQUEST['key'])) {
         engelsystem_error('Missing key.');
     }
 
diff --git a/includes/controller/shifttypes_controller.php b/includes/controller/shifttypes_controller.php
index e6ba716f..9a470e29 100644
--- a/includes/controller/shifttypes_controller.php
+++ b/includes/controller/shifttypes_controller.php
@@ -79,7 +79,7 @@ function shifttype_edit_controller()
             error(_('Please enter a name.'));
         }
 
-        if (isset($_REQUEST['angeltype_id']) && preg_match('/^[0-9]+$/', $_REQUEST['angeltype_id'])) {
+        if (isset($_REQUEST['angeltype_id']) && preg_match('/^\d+$/', $_REQUEST['angeltype_id'])) {
             $angeltype_id = $_REQUEST['angeltype_id'];
         } else {
             $angeltype_id = null;
diff --git a/includes/model/Message_model.php b/includes/model/Message_model.php
index a7da63b8..ebd4b37e 100644
--- a/includes/model/Message_model.php
+++ b/includes/model/Message_model.php
@@ -41,7 +41,7 @@ function Message_send($receiver_user_id, $text)
     global $user;
 
     $text = preg_replace("/([^\p{L}\p{P}\p{Z}\p{N}\n]{1,})/ui", '', strip_tags($text));
-    $receiver_user_id = preg_replace('/([^0-9]{1,})/ui', '', strip_tags($receiver_user_id));
+    $receiver_user_id = preg_replace('/([^\d]{1,})/ui', '', strip_tags($receiver_user_id));
 
     if (
         ($text != '' && is_numeric($receiver_user_id))
diff --git a/includes/pages/admin_active.php b/includes/pages/admin_active.php
index d3b290f9..275f50ba 100644
--- a/includes/pages/admin_active.php
+++ b/includes/pages/admin_active.php
@@ -33,7 +33,7 @@ function admin_active()
     if (isset($_REQUEST['set_active'])) {
         $valid = true;
 
-        if (isset($_REQUEST['count']) && preg_match('/^[0-9]+$/', $_REQUEST['count'])) {
+        if (isset($_REQUEST['count']) && preg_match('/^\d+$/', $_REQUEST['count'])) {
             $count = strip_request_item('count');
             if ($count < $forced_count) {
                 error(sprintf(
@@ -89,7 +89,7 @@ function admin_active()
         }
     }
 
-    if (isset($_REQUEST['active']) && preg_match('/^[0-9]+$/', $_REQUEST['active'])) {
+    if (isset($_REQUEST['active']) && preg_match('/^\d+$/', $_REQUEST['active'])) {
         $user_id = $_REQUEST['active'];
         $user_source = User($user_id);
         if ($user_source != null) {
@@ -99,7 +99,7 @@ function admin_active()
         } else {
             $msg = error(_('Angel not found.'), true);
         }
-    } elseif (isset($_REQUEST['not_active']) && preg_match('/^[0-9]+$/', $_REQUEST['not_active'])) {
+    } elseif (isset($_REQUEST['not_active']) && preg_match('/^\d+$/', $_REQUEST['not_active'])) {
         $user_id = $_REQUEST['not_active'];
         $user_source = User($user_id);
         if ($user_source != null) {
@@ -109,7 +109,7 @@ function admin_active()
         } else {
             $msg = error(_('Angel not found.'), true);
         }
-    } elseif (isset($_REQUEST['tshirt']) && preg_match('/^[0-9]+$/', $_REQUEST['tshirt'])) {
+    } elseif (isset($_REQUEST['tshirt']) && preg_match('/^\d+$/', $_REQUEST['tshirt'])) {
         $user_id = $_REQUEST['tshirt'];
         $user_source = User($user_id);
         if ($user_source != null) {
@@ -119,7 +119,7 @@ function admin_active()
         } else {
             $msg = error('Angel not found.', true);
         }
-    } elseif (isset($_REQUEST['not_tshirt']) && preg_match('/^[0-9]+$/', $_REQUEST['not_tshirt'])) {
+    } elseif (isset($_REQUEST['not_tshirt']) && preg_match('/^\d+$/', $_REQUEST['not_tshirt'])) {
         $user_id = $_REQUEST['not_tshirt'];
         $user_source = User($user_id);
         if ($user_source != null) {
diff --git a/includes/pages/admin_arrive.php b/includes/pages/admin_arrive.php
index 0080ccf9..77155dae 100644
--- a/includes/pages/admin_arrive.php
+++ b/includes/pages/admin_arrive.php
@@ -21,7 +21,7 @@ function admin_arrive()
         $search = strip_request_item('search');
     }
 
-    if (isset($_REQUEST['reset']) && preg_match('/^[0-9]*$/', $_REQUEST['reset'])) {
+    if (isset($_REQUEST['reset']) && preg_match('/^\d*$/', $_REQUEST['reset'])) {
         $user_id = $_REQUEST['reset'];
         $user_source = User($user_id);
         if ($user_source != null) {
@@ -37,7 +37,7 @@ function admin_arrive()
         } else {
             $msg = error(_('Angel not found.'), true);
         }
-    } elseif (isset($_REQUEST['arrived']) && preg_match('/^[0-9]*$/', $_REQUEST['arrived'])) {
+    } elseif (isset($_REQUEST['arrived']) && preg_match('/^\d*$/', $_REQUEST['arrived'])) {
         $user_id = $_REQUEST['arrived'];
         $user_source = User($user_id);
         if ($user_source != null) {
diff --git a/includes/pages/admin_groups.php b/includes/pages/admin_groups.php
index 104fa274..4011ccf1 100644
--- a/includes/pages/admin_groups.php
+++ b/includes/pages/admin_groups.php
@@ -53,7 +53,7 @@ function admin_groups()
     } else {
         switch ($_REQUEST['action']) {
             case 'edit':
-                if (isset($_REQUEST['id']) && preg_match('/^-[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^-\d{1,11}$/', $_REQUEST['id'])) {
                     $group_id = $_REQUEST['id'];
                 } else {
                     return error('Incomplete call, missing Groups ID.', true);
@@ -99,7 +99,7 @@ function admin_groups()
                 break;
 
             case 'save':
-                if (isset($_REQUEST['id']) && preg_match('/^-[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^-\d{1,11}$/', $_REQUEST['id'])) {
                     $group_id = $_REQUEST['id'];
                 } else {
                     return error('Incomplete call, missing Groups ID.', true);
@@ -114,7 +114,7 @@ function admin_groups()
                     DB::delete('DELETE FROM `GroupPrivileges` WHERE `group_id`=?', [$group_id]);
                     $privilege_names = [];
                     foreach ($_REQUEST['privileges'] as $privilege) {
-                        if (preg_match('/^[0-9]{1,}$/', $privilege)) {
+                        if (preg_match('/^\d{1,}$/', $privilege)) {
                             $group_privileges_source = DB::select(
                                 'SELECT `name` FROM `Privileges` WHERE `id`=? LIMIT 1',
                                 [$privilege]
diff --git a/includes/pages/admin_news.php b/includes/pages/admin_news.php
index af5dffc6..a814bc33 100644
--- a/includes/pages/admin_news.php
+++ b/includes/pages/admin_news.php
@@ -14,7 +14,7 @@ function admin_news()
     }
 
     $html = '<div class="col-md-12"><h1>' . _('Edit news entry') . '</h1>' . msg();
-    if (isset($_REQUEST['id']) && preg_match('/^[0-9]{1,11}$/', $_REQUEST['id'])) {
+    if (isset($_REQUEST['id']) && preg_match('/^\d{1,11}$/', $_REQUEST['id'])) {
         $news_id = $_REQUEST['id'];
     } else {
         return error('Incomplete call, missing News ID.', true);
diff --git a/includes/pages/admin_questions.php b/includes/pages/admin_questions.php
index aca9b570..4c84e4f8 100644
--- a/includes/pages/admin_questions.php
+++ b/includes/pages/admin_questions.php
@@ -98,7 +98,7 @@ function admin_questions()
     } else {
         switch ($_REQUEST['action']) {
             case 'answer':
-                if (isset($_REQUEST['id']) && preg_match('/^[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^\d{1,11}$/', $_REQUEST['id'])) {
                     $question_id = $_REQUEST['id'];
                 } else {
                     return error('Incomplete call, missing Question ID.', true);
@@ -139,7 +139,7 @@ function admin_questions()
                 }
                 break;
             case 'delete':
-                if (isset($_REQUEST['id']) && preg_match('/^[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^\d{1,11}$/', $_REQUEST['id'])) {
                     $question_id = $_REQUEST['id'];
                 } else {
                     return error('Incomplete call, missing Question ID.', true);
diff --git a/includes/pages/admin_rooms.php b/includes/pages/admin_rooms.php
index 50be15f3..d483f99e 100644
--- a/includes/pages/admin_rooms.php
+++ b/includes/pages/admin_rooms.php
@@ -112,7 +112,7 @@ function admin_rooms()
                 foreach ($angeltypes as $angeltype_id => $angeltype) {
                     if (
                         isset($_REQUEST['angeltype_count_' . $angeltype_id])
-                        && preg_match('/^[0-9]{1,4}$/', $_REQUEST['angeltype_count_' . $angeltype_id])
+                        && preg_match('/^\d{1,4}$/', $_REQUEST['angeltype_count_' . $angeltype_id])
                     ) {
                         $angeltypes_count[$angeltype_id] = $_REQUEST['angeltype_count_' . $angeltype_id];
                     } else {
diff --git a/includes/pages/admin_shifts.php b/includes/pages/admin_shifts.php
index c543e827..06071233 100644
--- a/includes/pages/admin_shifts.php
+++ b/includes/pages/admin_shifts.php
@@ -72,7 +72,7 @@ function admin_shifts()
         // Auswahl der sichtbaren Locations für die Schichten
         if (
             isset($_REQUEST['rid'])
-            && preg_match('/^[0-9]+$/', $_REQUEST['rid'])
+            && preg_match('/^\d+$/', $_REQUEST['rid'])
             && isset($room_array[$_REQUEST['rid']])
         ) {
             $rid = $_REQUEST['rid'];
@@ -105,7 +105,7 @@ function admin_shifts()
             if ($_REQUEST['mode'] == 'single') {
                 $mode = 'single';
             } elseif ($_REQUEST['mode'] == 'multi') {
-                if (isset($_REQUEST['length']) && preg_match('/^[0-9]+$/', trim($_REQUEST['length']))) {
+                if (isset($_REQUEST['length']) && preg_match('/^\d+$/', trim($_REQUEST['length']))) {
                     $mode = 'multi';
                     $length = trim($_REQUEST['length']);
                 } else {
@@ -115,7 +115,7 @@ function admin_shifts()
             } elseif ($_REQUEST['mode'] == 'variable') {
                 if (
                     isset($_REQUEST['change_hours'])
-                    && preg_match('/^([0-9]{2}(,|$))/', trim(str_replace(' ', '', $_REQUEST['change_hours'])))
+                    && preg_match('/^(\d{2}(,|$))/', trim(str_replace(' ', '', $_REQUEST['change_hours'])))
                 ) {
                     $mode = 'variable';
                     $change_hours = array_map('trim', explode(',', $_REQUEST['change_hours']));
@@ -137,7 +137,7 @@ function admin_shifts()
                 foreach ($types as $type) {
                     if (
                         isset($_REQUEST['type_' . $type['id']])
-                        && preg_match('/^[0-9]+$/', trim($_REQUEST['type_' . $type['id']]))
+                        && preg_match('/^\d+$/', trim($_REQUEST['type_' . $type['id']]))
                     ) {
                         $needed_angel_types[$type['id']] = trim($_REQUEST['type_' . $type['id']]);
                     } else {
diff --git a/includes/pages/guest_login.php b/includes/pages/guest_login.php
index 647fa585..66a06116 100644
--- a/includes/pages/guest_login.php
+++ b/includes/pages/guest_login.php
@@ -155,7 +155,7 @@ function guest_register()
         if (isset($_REQUEST['prename'])) {
             $preName = strip_request_item('prename');
         }
-        if (isset($_REQUEST['age']) && preg_match('/^[0-9]{0,4}$/', $_REQUEST['age'])) {
+        if (isset($_REQUEST['age']) && preg_match('/^\d{0,4}$/', $_REQUEST['age'])) {
             $age = strip_request_item('age');
         }
         if (isset($_REQUEST['tel'])) {
diff --git a/includes/pages/user_atom.php b/includes/pages/user_atom.php
index 04edf03f..3c4b631d 100644
--- a/includes/pages/user_atom.php
+++ b/includes/pages/user_atom.php
@@ -9,7 +9,7 @@ function user_atom()
 {
     global $user, $display_news;
 
-    if (!isset($_REQUEST['key']) || !preg_match('/^[0-9a-f]{32}$/', $_REQUEST['key'])) {
+    if (!isset($_REQUEST['key']) || !preg_match('/^[\da-f]{32}$/', $_REQUEST['key'])) {
         engelsystem_error('Missing key.');
     }
     $key = $_REQUEST['key'];
@@ -48,7 +48,7 @@ function make_atom_entries_from_news($news_entries)
   <title>Engelsystem</title>
   <id>' . $_SERVER['HTTP_HOST']
         . htmlspecialchars(preg_replace(
-            '#[&?]key=[a-f0-9]{32}#',
+            '#[&?]key=[a-f\d]{32}#',
             '',
             $_SERVER['REQUEST_URI']
         ))
diff --git a/includes/pages/user_ical.php b/includes/pages/user_ical.php
index f9c364e6..ce474a9e 100644
--- a/includes/pages/user_ical.php
+++ b/includes/pages/user_ical.php
@@ -7,7 +7,7 @@ function user_ical()
 {
     global $user;
 
-    if (!isset($_REQUEST['key']) || !preg_match('/^[0-9a-f]{32}$/', $_REQUEST['key'])) {
+    if (!isset($_REQUEST['key']) || !preg_match('/^[\da-f]{32}$/', $_REQUEST['key'])) {
         engelsystem_error('Missing key.');
     }
     $key = $_REQUEST['key'];
diff --git a/includes/pages/user_messages.php b/includes/pages/user_messages.php
index e4669411..dd22cd66 100644
--- a/includes/pages/user_messages.php
+++ b/includes/pages/user_messages.php
@@ -123,7 +123,7 @@ function user_messages()
     } else {
         switch ($_REQUEST['action']) {
             case 'read':
-                if (isset($_REQUEST['id']) && preg_match('/^[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^\d{1,11}$/', $_REQUEST['id'])) {
                     $message_id = $_REQUEST['id'];
                 } else {
                     return error(_('Incomplete call, missing Message ID.'), true);
@@ -145,7 +145,7 @@ function user_messages()
                 break;
 
             case 'delete':
-                if (isset($_REQUEST['id']) && preg_match('/^[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^\d{1,11}$/', $_REQUEST['id'])) {
                     $message_id = $_REQUEST['id'];
                 } else {
                     return error(_('Incomplete call, missing Message ID.'), true);
diff --git a/includes/pages/user_myshifts.php b/includes/pages/user_myshifts.php
index 76b79032..acb78875 100644
--- a/includes/pages/user_myshifts.php
+++ b/includes/pages/user_myshifts.php
@@ -23,7 +23,7 @@ function user_myshifts()
     if (
         isset($_REQUEST['id'])
         && in_array('user_shifts_admin', $privileges)
-        && preg_match('/^[0-9]{1,}$/', $_REQUEST['id'])
+        && preg_match('/^\d{1,}$/', $_REQUEST['id'])
         && count(DB::select('SELECT `UID` FROM `User` WHERE `UID`=?', [$_REQUEST['id']])) > 0
     ) {
         $user_id = $_REQUEST['id'];
@@ -47,7 +47,7 @@ function user_myshifts()
             ),
             button(page_link_to('user_myshifts') . '&reset=ack', _('Continue'), 'btn-danger')
         ]);
-    } elseif (isset($_REQUEST['edit']) && preg_match('/^[0-9]*$/', $_REQUEST['edit'])) {
+    } elseif (isset($_REQUEST['edit']) && preg_match('/^\d*$/', $_REQUEST['edit'])) {
         $user_id = $_REQUEST['edit'];
         $shift = DB::select('
                 SELECT
@@ -129,7 +129,7 @@ function user_myshifts()
         } else {
             redirect(page_link_to('user_myshifts'));
         }
-    } elseif (isset($_REQUEST['cancel']) && preg_match('/^[0-9]*$/', $_REQUEST['cancel'])) {
+    } elseif (isset($_REQUEST['cancel']) && preg_match('/^\d*$/', $_REQUEST['cancel'])) {
         $user_id = $_REQUEST['cancel'];
         $shift = DB::select('
                 SELECT *
diff --git a/includes/pages/user_news.php b/includes/pages/user_news.php
index 7dfc7d0c..69d20e69 100644
--- a/includes/pages/user_news.php
+++ b/includes/pages/user_news.php
@@ -35,7 +35,7 @@ function user_meetings()
 
     $html = '<div class="col-md-12"><h1>' . meetings_title() . '</h1>' . msg();
 
-    if (isset($_REQUEST['page']) && preg_match('/^[0-9]{1,}$/', $_REQUEST['page'])) {
+    if (isset($_REQUEST['page']) && preg_match('/^\d{1,}$/', $_REQUEST['page'])) {
         $page = $_REQUEST['page'];
     } else {
         $page = 0;
@@ -120,7 +120,7 @@ function user_news_comments()
     $html = '<div class="col-md-12"><h1>' . user_news_comments_title() . '</h1>';
     if (
         isset($_REQUEST['nid'])
-        && preg_match('/^[0-9]{1,}$/', $_REQUEST['nid'])
+        && preg_match('/^\d{1,}$/', $_REQUEST['nid'])
         && count(DB::select('SELECT `ID` FROM `News` WHERE `ID`=? LIMIT 1', [$_REQUEST['nid']])) > 0
     ) {
         $nid = $_REQUEST['nid'];
@@ -203,7 +203,7 @@ function user_news()
         redirect(page_link_to('news'));
     }
 
-    if (isset($_REQUEST['page']) && preg_match('/^[0-9]{1,}$/', $_REQUEST['page'])) {
+    if (isset($_REQUEST['page']) && preg_match('/^\d{1,}$/', $_REQUEST['page'])) {
         $page = $_REQUEST['page'];
     } else {
         $page = 0;
diff --git a/includes/pages/user_questions.php b/includes/pages/user_questions.php
index 04ae8914..5cb60db3 100644
--- a/includes/pages/user_questions.php
+++ b/includes/pages/user_questions.php
@@ -56,7 +56,7 @@ function user_questions()
                 }
                 break;
             case 'delete':
-                if (isset($_REQUEST['id']) && preg_match('/^[0-9]{1,11}$/', $_REQUEST['id'])) {
+                if (isset($_REQUEST['id']) && preg_match('/^\d{1,11}$/', $_REQUEST['id'])) {
                     $question_id = $_REQUEST['id'];
                 } else {
                     return error(_('Incomplete call, missing Question ID.'), true);
diff --git a/includes/sys_page.php b/includes/sys_page.php
index fd03e291..b2199988 100644
--- a/includes/sys_page.php
+++ b/includes/sys_page.php
@@ -164,7 +164,7 @@ function strip_request_item($name, $default_value = null)
 function test_request_int($name)
 {
     if (isset($_REQUEST[$name])) {
-        return preg_match('/^[0-9]*$/', $_REQUEST[$name]);
+        return preg_match('/^\d*$/', $_REQUEST[$name]);
     }
     return false;
 }
diff --git a/public/index.php b/public/index.php
index 92a71c6d..12d6f744 100644
--- a/public/index.php
+++ b/public/index.php
@@ -30,7 +30,7 @@ if (!isset($_REQUEST['p'])) {
 
 if (
     isset($_REQUEST['p'])
-    && preg_match('/^[a-z0-9_]*$/i', $_REQUEST['p'])
+    && preg_match('/^\w*$/i', $_REQUEST['p'])
     && (
         in_array($_REQUEST['p'], $free_pages)
         || (isset($privileges) && in_array($_REQUEST['p'], $privileges))