diff --git a/NEXT_STEPS.md b/NEXT_STEPS.md
index 4eed752..4d459d4 100644
--- a/NEXT_STEPS.md
+++ b/NEXT_STEPS.md
@@ -2,15 +2,6 @@
 
 ## Issue Drafts (Ready for Gitea/GitHub)
 
-- #TODO Enable strict types + typed signatures
-- Aufwand: `M`
-- Labels: `quality`, `refactor`
-- Ziel: Konsistente Typen und weniger implizite Typfehler.
-- Akzeptanzkriterien:
-- Alle PHP-Dateien starten mit `declare(strict_types=1);` (wo kompatibel).
-- Oeffentliche Funktionen erhalten Rueckgabe-/Parameter-Typen.
-- Inkompatible Stellen sind dokumentiert oder angepasst.
-
 - #TODO Define unified error strategy
 - Aufwand: `M`
 - Labels: `quality`, `api`
diff --git a/_func.php b/_func.php
index d11c170..923b46b 100644
--- a/_func.php
+++ b/_func.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 // include ('config.php');
 include_once ('sql.php');
 $sql = new SQL ();
@@ -8,4 +9,4 @@ include_once ('mail.php');
 include_once ('debug.php');
 include_once ('troy-api.php');
 // include_once ('markdown.php');
-?>
\ No newline at end of file
+?>
diff --git a/debug.php b/debug.php
index ac60ed5..978f063 100644
--- a/debug.php
+++ b/debug.php
@@ -1,14 +1,16 @@
 <?php 
-    function debug($s) {
+    declare(strict_types=1);
+
+    function debug(mixed $s): void {
         if(isset($_COOKIE['debug'])) 
             print_r($s);
     }
     
-    function debugCookie($on=true) {
+    function debugCookie(bool $on = true): void {
         if($on) {
             setcookie('debug','1',time()+(60*60*24*365),"/");
         }else{
             setcookie('debug',null,0,"/");
         }
     }
-?>
\ No newline at end of file
+?>
diff --git a/ips/crawler.php b/ips/crawler.php
index 6de1b40..f75696e 100644
--- a/ips/crawler.php
+++ b/ips/crawler.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 $_ips_crawler = array (
         '34.79.234.76', // google
         '40.77.167.', // bing bot
@@ -28,7 +30,7 @@ $_ips_crawler = array (
         '2a01:4f8:190:4244::2', // mj12bot
         '2a01:4f8:162:43c5::2', // mj12bot
 );
-function checkHuman() {
+function checkHuman(): bool {
   global $_ips_crawler;
   if (stripos ( $_SERVER ['HTTP_USER_AGENT'], 'bot' ) !== false || stripos ( $_SERVER ['HTTP_USER_AGENT'], 'crawler' ) !== false) {
     return false;
@@ -40,4 +42,4 @@ function checkHuman() {
   }
   return true;
 }
-?>
\ No newline at end of file
+?>
diff --git a/link-meta.php b/link-meta.php
index a92db62..6c1b249 100644
--- a/link-meta.php
+++ b/link-meta.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 function httpContext(int $timeout = 8) {
     return stream_context_create([
@@ -158,11 +159,7 @@ function getPageInfo(string $url): array {
     return $ret;
 }
 
-function sanitizeTags($input): array {
-    if (!is_array($input)) {
-        return [];
-    }
-
+function sanitizeTags(array $input): array {
     $ret = [];
     foreach ($input as $tag) {
         if (!is_string($tag)) {
diff --git a/mail.php b/mail.php
index d770dec..4510b23 100644
--- a/mail.php
+++ b/mail.php
@@ -1,5 +1,7 @@
 <?php
-function send_mail($an, $betreff, $text, $ok = '', $error = '') {
+declare(strict_types=1);
+
+function send_mail(string $an, string $betreff, string $text, string $ok = '', string $error = ''): void {
   global $absender;
   $sender = 'noreply@troy-grunt.de';
   if(isset($absender) && $absender) {
@@ -23,7 +25,7 @@ function send_mail($an, $betreff, $text, $ok = '', $error = '') {
   }
 }
 
-function send_html_mail($an, $betreff, $text, $ok = '', $error = '') {
+function send_html_mail(string $an, string $betreff, string $text, string $ok = '', string $error = ''): void {
   global $absender;
   $sender = 'noreply@troy-grunt.de';
   if(isset($absender) && $absender) {
@@ -57,7 +59,7 @@ function send_html_mail($an, $betreff, $text, $ok = '', $error = '') {
   }
 }
 
-function send_php_mail($an, $betreff, $text, $ok = '', $error = '') {
+function send_php_mail(string $an, string $betreff, string $text, string $ok = '', string $error = ''): void {
   global $_sendermail;
   $sender = 'noreply@troy-grunt.de';
   if (isset ( $_sendermail )) {
@@ -78,4 +80,4 @@ function send_php_mail($an, $betreff, $text, $ok = '', $error = '') {
       echo 'Message sent!';
   }
 }
-?>
\ No newline at end of file
+?>
diff --git a/markdown.php b/markdown.php
index 0d90701..3a77050 100644
--- a/markdown.php
+++ b/markdown.php
@@ -1,6 +1,7 @@
 <?php
+declare(strict_types=1);
 // TODO markdown imple
-function md($str) {
+function md(string $str): string {
   // return nl2br ( $str ); // TODO md problem
   $text = '<p>';
   $lv = 0;
@@ -75,10 +76,10 @@ function md($str) {
   $text .= '</p>';
   return $text;
 }
-function _md_link_replacer($in) {
+function _md_link_replacer(array $in): string {
   // var_dump ( $in );
   $in = explode ( '|', $in [1], 2 );
 
   return '<a href="' . $in [0] . '" target="_blank">' . (isset ( $in [1] ) ? $in [1] : $in [0]) . '</a>';
 }
-?>
\ No newline at end of file
+?>
diff --git a/numbers.php b/numbers.php
index 7f97f26..25c99b4 100644
--- a/numbers.php
+++ b/numbers.php
@@ -1,5 +1,7 @@
 <?php
-function decade($zahl)
+declare(strict_types=1);
+
+function decade(int|float|string $zahl): int|float|string
 {
     if (! is_numeric($zahl) || $zahl == 0)
         return $zahl;
@@ -31,7 +33,7 @@ function decade($zahl)
         return $zahl . ' ' . $si[$e];
 }
 
-function onlyNumeric($num) {
+function onlyNumeric(string $num): string {
     return preg_replace("/[^0-9\.\-]+/", "", $num);
 }
-?>
\ No newline at end of file
+?>
diff --git a/og.php b/og.php
index fb644d4..24a2add 100644
--- a/og.php
+++ b/og.php
@@ -1,5 +1,7 @@
 <?php
-function scanOG($url) {
+declare(strict_types=1);
+
+function scanOG(string $url): array {
   $og = array();
   $html = file_get_contents($url);
 
@@ -12,4 +14,4 @@ function scanOG($url) {
   //print_r($og);
   return $og;
 }
-?>
\ No newline at end of file
+?>
diff --git a/secret.php.example b/secret.php.example
index 1077fb5..0052050 100644
--- a/secret.php.example
+++ b/secret.php.example
@@ -1,15 +1,17 @@
-<?php
-if (!defined('SQL_LOG')) define ( 'SQL_LOG', 1 ); // schreibt sql querys in eine log
-
-$_m['host'] = 'localhost';
-$_m['user'] = '';
-$_m['pass'] = '';
-$_m['data'] = '';
-$_m['pre']  = '';
-$_m['salt'] = '';
-
-$_sendermail = 'noreply@.de';
-$_smtp['srv'] = 'mail.seemsleg.it';
-$_smtp['user'] = 'noreply@.de';
-$_smtp['pw'] = '';
-?>
\ No newline at end of file
+<?php
+declare(strict_types=1);
+
+if (!defined('SQL_LOG')) define ( 'SQL_LOG', 1 ); // schreibt sql querys in eine log
+
+$_m['host'] = 'localhost';
+$_m['user'] = '';
+$_m['pass'] = '';
+$_m['data'] = '';
+$_m['pre']  = '';
+$_m['salt'] = '';
+
+$_sendermail = 'noreply@.de';
+$_smtp['srv'] = 'mail.seemsleg.it';
+$_smtp['user'] = 'noreply@.de';
+$_smtp['pw'] = '';
+?>
diff --git a/sql.php b/sql.php
index e0ae57e..2f3c4d3 100644
--- a/sql.php
+++ b/sql.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 class SQL {
   private $h;
   private $res = false;
@@ -22,7 +24,7 @@ class SQL {
     }
     return true;
   }
-  public function get($que, $t = '', $p = array ()) {
+  public function get(string $que, string $t = '', mixed $p = array ()): array|false {
     // echo $que;
     $this->cnt_get ++;
     if (SQL_LOG)
@@ -89,14 +91,14 @@ class SQL {
     }
     return $ret;
   }
-  public function single($que, $t = '', $p = array ()) {
+  public function single(string $que, string $t = '', mixed $p = array ()): array|false {
     $data = $this->get ( $que, $t, $p );
     if ($data) {
       return $data [0];
     }
     return false;
   }
-  public function list($que, $t = '', $p = array ()) {
+  public function list(string $que, string $t = '', mixed $p = array ()): array|false {
     $data = $this->get ( $que, $t, $p );
     if ($data) {
       $ret = array ();
@@ -109,7 +111,7 @@ class SQL {
     }
     return false;
   }
-  public function keyval($que, $k, $v, $t = '', $p = array ()) {
+  public function keyval(string $que, string|int $k, string|int $v, string $t = '', mixed $p = array ()): array|false {
     $data = $this->get ( $que, $t, $p );
     if ($data) {
       $ret = array ();
@@ -120,7 +122,7 @@ class SQL {
     }
     return false;
   }
-  public function set($que, $t = '', $p = array (), $id = false) {
+  public function set(string $que, string $t = '', mixed $p = array (), bool $id = false): int|false {
     // echo $que;
     $this->cnt_set ++;
     $statement = $this->h->prepare ( $que );
@@ -189,7 +191,7 @@ class SQL {
       return $statement->affected_rows;
     }
   }
-  function __destruct() {
+  function __destruct(): void {
     if (SQL_LOG)
       $this->h->close ();
     // echo 'DESTROY';
diff --git a/string.php b/string.php
index f0b6137..8af8939 100644
--- a/string.php
+++ b/string.php
@@ -1,5 +1,7 @@
 <?php
-function umlaute($str) {
+declare(strict_types=1);
+
+function umlaute(string $str): string {
   return str_replace ( array (
           'Ä',
           'Ö',
@@ -20,10 +22,10 @@ function umlaute($str) {
           '&amp;'
   ), $str );
 }
-function chk($str) {
+function chk(string $str): string {
   return str_replace ( "'", '"', $str );
 }
-function noScript($str) {
+function noScript(string $str): string {
   return str_replace ( array (
           '<',
           '>'
@@ -32,7 +34,7 @@ function noScript($str) {
           '&gt;'
   ), $str );
 }
-function random($name_laenge) {
+function random(int $name_laenge): string {
   $zeichen = "abcedfghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRTSUVWXYZ0123456789";
   $name_neu = "";
 
@@ -43,32 +45,32 @@ function random($name_laenge) {
   }
   return $name_neu;
 }
-function startsWith($haystack, $needle) {
+function startsWith(string $haystack, string $needle): bool {
   $length = strlen ( $needle );
   return (substr ( $haystack, 0, $length ) === $needle);
 }
-function endsWith($haystack, $needle) {
+function endsWith(string $haystack, string $needle): bool {
   $length = strlen ( $needle );
 
   return $length === 0 || (substr ( $haystack, - $length ) === $needle);
 }
-function onlyAlpha($str, $zus = '') {
+function onlyAlpha(string $str, string $zus = ''): string {
   return preg_replace ( "/[^a-zA-Z0-9 \-\{$zus}_]+/", "", $str );
 }
-function shortener($str, $len = 50, $fill = '...') {
+function shortener(string $str, int $len = 50, string $fill = '...'): string {
   if (strlen ( $str ) > $len) {
     $str = substr ( $str, 0, $len - strlen ( $fill ) ) . $fill;
   }
   return $str;
 }
-function isEmail($str) {
+function isEmail(string $str): string|false {
   $match = preg_match ( "/[a-zA-Z0-9\-\_\.]*\@[a-zA-Z0-9\-\_\.]*.[a-z]{2,10}/", $str );
   if ($match) {
     return $str;
   }
   return false;
 }
-function markUp($text) {
+function markUp(string $text): string {
   $r = '';
   $lv = 0;
   foreach ( explode ( "\n", $text ) as $t ) {
@@ -127,7 +129,7 @@ function markUp($text) {
   }
   return $r;
 }
-function onlySimpleHTML($s) {
+function onlySimpleHTML(string $s): string {
   $s = str_replace ( array (
           '<',
           '>'
@@ -259,14 +261,14 @@ function onlySimpleHTML($s) {
 
   return $s;
 }
-function linkify($input) {
+function linkify(string $input): string {
   $pattern = '@(http(s)?://[a-zA-Z0-9/\.\#\-\_]*)@';
   return $output = preg_replace ( $pattern, '<a href="$1">$1</a>', $input );
 }
-function inStr($needle, $haystack) {
+function inStr(string $needle, string $haystack): bool {
   if (strpos ( $haystack, $needle ) !== false) {
     return true;
   }
   return false;
 }
-?>
\ No newline at end of file
+?>
diff --git a/troy-api.php b/troy-api.php
index 8540d40..64e6e42 100644
--- a/troy-api.php
+++ b/troy-api.php
@@ -1,5 +1,7 @@
 <?php
-function sendToTroy($data) {
+declare(strict_types=1);
+
+function sendToTroy(array $data): string|false {
   $url = 'https://troy-grunt.de/api.php';
   $options = array (
           'http' => array (
@@ -14,7 +16,7 @@ function sendToTroy($data) {
   return file_get_contents ( $url, false, $context );
 }
 
-function sendToGitea($title, $message) {
+function sendToGitea(string $title, string $message): array|null {
     // secret.php liegt in lib/
     require 'secret.php';