diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index 40d0847678..c76d76095e 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -43,6 +43,7 @@
         'switch_case_space' => true,
         'trim_array_spaces' => true,
         'visibility_required' => true,
+        'void_return' => true,
         'whitespace_after_comma_in_array' => true,
     ]);
 
diff --git a/include/changelogs.inc b/include/changelogs.inc
index 22c346a0ae..a3317ab03d 100644
--- a/include/changelogs.inc
+++ b/include/changelogs.inc
@@ -1,33 +1,33 @@
 <?php
-function bugfix($number) {
+function bugfix($number): void {
     echo "Fixed bug "; bugl($number);
 }
 
-function bugl($number) {
+function bugl($number): void {
     echo "<a href=\"http://bugs.php.net/$number\">#$number</a>";
 }
 
-function implemented($number) {
+function implemented($number): void {
     echo "Implemented FR "; bugl($number);
 }
 
-function peclbugfix($number) {
+function peclbugfix($number): void {
     echo "Fixed PECL bug "; bugl($number);
 }
 
-function peclbugl($number) {
+function peclbugl($number): void {
     echo "<a href=\"http://pecl.php.net/bugs/bug.php?id=$number\">#$number</a>";
 }
 
-function githubissue($repo, $number) {
+function githubissue($repo, $number): void {
     echo "Fixed issue "; githubissuel($repo, $number);
 }
 
-function githubissuel($repo, $number) {
+function githubissuel($repo, $number): void {
     echo "<a href=\"https://github.com/$repo/issues/$number\">GH-$number</a>";
 }
 
-function release_date($in) {
+function release_date($in): void {
     $time = strtotime($in);
     $human_readable = date('d M Y', $time);
     $for_tools = date('Y-m-d', $time);
diff --git a/include/do-download.inc b/include/do-download.inc
index 9c767ce5ee..b31f763b2c 100644
--- a/include/do-download.inc
+++ b/include/do-download.inc
@@ -23,7 +23,7 @@ function get_actual_download_file($file)
     return $found;
 }
 // Download a file from a mirror site
-function download_file($mirror, $file)
+function download_file($mirror, $file): void
 {
     // Redirect to the particular file
     if (!headers_sent()) {
diff --git a/include/errors.inc b/include/errors.inc
index 93a1840bc4..ac5d2586d3 100644
--- a/include/errors.inc
+++ b/include/errors.inc
@@ -6,7 +6,7 @@
 */
 
 // A 'good looking' 404 error message page
-function error_404()
+function error_404(): void
 {
     global $MYSITE;
     status_header(404);
@@ -19,7 +19,7 @@ function error_404()
 }
 
 // A 'good looking' 404 error message page for manual pages
-function error_404_manual()
+function error_404_manual(): void
 {
     global $MYSITE;
     status_header(404);
@@ -35,7 +35,7 @@ function error_404_manual()
 }
 
 // An error message page for manual pages from inactive languages
-function error_inactive_manual_page($lang_name, $en_page)
+function error_inactive_manual_page($lang_name, $en_page): void
 {
     global $MYSITE, $ACTIVE_ONLINE_LANGUAGES;
     status_header(404);
@@ -61,7 +61,7 @@ function error_inactive_manual_page($lang_name, $en_page)
 }
 
 // This service is not working right now
-function error_noservice()
+function error_noservice(): void
 {
     global $MYSITE;
     site_header('Service not working', ["noindex"]);
@@ -76,7 +76,7 @@ function error_noservice()
 }
 
 // There is no such mirror
-function error_nomirror($mirror) {
+function error_nomirror($mirror): void {
     site_header("No such mirror", ["noindex"]);
     echo "<h1>No such mirror</h1>\n<p>The mirror you tried to access (" .
          htmlspecialchars($mirror) .
diff --git a/include/layout.inc b/include/layout.inc
index 7378d66ec1..563ed8bade 100644
--- a/include/layout.inc
+++ b/include/layout.inc
@@ -48,10 +48,10 @@ function highlight_php_trimmed($code, $return = false)
 }
 
 // Stats pages still need this
-function commonHeader($title) { site_header($title); }
+function commonHeader($title): void { site_header($title); }
 
 // Stats pages still need this
-function commonFooter() { site_footer(); }
+function commonFooter(): void { site_footer(); }
 
 // Resize the image using the output of make_image()
 function resize_image($img, $width = 1, $height = 1)
@@ -105,7 +105,7 @@ function make_image($file, $alt = false, $align = false, $extras = false,
 
 // Print an <img> tag out for a given file
 function print_image($file, $alt = false, $align = false, $extras = false,
-                     $dir = '/images')
+                     $dir = '/images'): void
 {
     echo make_image($file, $alt, $align, $extras, $dir);
 }
@@ -163,12 +163,12 @@ function make_popup_link ($url, $linktext = false, $target = false, $windowprops
 // print_popup_link()
 // print a hyperlink to something, within the site, that pops up a new window
 //
-function print_popup_link($url, $linktext = false, $windowprops = "", $target = false, $extras = false) {
+function print_popup_link($url, $linktext = false, $windowprops = "", $target = false, $extras = false): void {
     echo make_popup_link($url, $linktext, $windowprops, $target, $extras);
 }
 
 // Print a link for a downloadable file (including filesize)
-function download_link($file, $title)
+function download_link($file, $title): void
 {
     $download_link = "/distributions/" . $file;
 
@@ -236,7 +236,7 @@ function clean_note($text)
     );
 }
 
-function display_errors($errors)
+function display_errors($errors): void
 {
     echo '<div class="errors">';
     if (count($errors) > 1) {
@@ -254,7 +254,7 @@ function display_errors($errors)
 
 // Displays an event. Used in event submission
 // previews and event information displays
-function display_event($event, $include_date = 1)
+function display_event($event, $include_date = 1): void
 {
     global $COUNTRIES;
     // Current month (int)($_GET['cm'] ?: 0)
@@ -354,7 +354,7 @@ function display_event($event, $include_date = 1)
 }
 
 // Print news links for archives
-function news_archive_sidebar()
+function news_archive_sidebar(): void
 {
     global $SIDEBAR_DATA;
     $SIDEBAR_DATA = '
@@ -447,7 +447,7 @@ EOT;
     return $retval;
 }
 
-function site_header($title = 'Hypertext Preprocessor', $config = [])
+function site_header($title = 'Hypertext Preprocessor', $config = []): void
 {
     global $MYSITE;
 
@@ -481,7 +481,7 @@ function site_header($title = 'Hypertext Preprocessor', $config = [])
 
     require __DIR__ . "/header.inc";
 }
-function site_footer($config = [])
+function site_footer($config = []): void
 {
     require __DIR__ . "/footer.inc";
 }
@@ -511,7 +511,7 @@ function get_news_changes()
     return false;
 }
 
-function news_toc($sections = null) {
+function news_toc($sections = null): void {
     include __DIR__ . "/pregen-news.inc";
     $items = [
         "news" => [
@@ -544,7 +544,7 @@ function news_toc($sections = null) {
         }
     }
 }
-function doc_toc($lang) {
+function doc_toc($lang): void {
     $file = __DIR__ . "/../manual/$lang/toc/index.inc";
     if (!file_exists($file)) {
         $lang = "en"; // Fallback on english if the translation doesn't exist
@@ -591,7 +591,7 @@ function doc_toc($lang) {
     echo "</dl>";
 
 }
-function doc_toc_list($lang, $index, $file) {
+function doc_toc_list($lang, $index, $file): void {
     include __DIR__ . "/../manual/$lang/toc/$file.inc";
 
     doc_toc_title($lang, $index, $file);
@@ -599,7 +599,7 @@ function doc_toc_list($lang, $index, $file) {
         echo "\t<dd><a href='/manual/$lang/{$entry[0]}'>{$entry[1]}</a></dd>\n";
     }
 }
-function doc_toc_title($lang, $index, $file, $elm = "dt") {
+function doc_toc_title($lang, $index, $file, $elm = "dt"): void {
     foreach ($index as $entry) {
         if ($entry[0] == "$file.php") {
             $link = $entry[0];
diff --git a/include/prepend.inc b/include/prepend.inc
index 13f901dff1..c6f03a4d5d 100644
--- a/include/prepend.inc
+++ b/include/prepend.inc
@@ -15,7 +15,7 @@ header("Content-type: text/html; charset=utf-8");
 header("Permissions-Policy: interest-cohort=()");
 
 /* Fix Silly Same Origin Policies */
-(function () {
+(function (): void {
     if (!isset($_SERVER["HTTP_ORIGIN"])) {
         return;
     }
@@ -94,7 +94,7 @@ include __DIR__ . '/last_updated.inc';
 // -----------------------------------------------------------------------------
 
 // Load in the user preferences
-function myphpnet_load()
+function myphpnet_load(): void
 {
     global $MYPHPNET, $MYSITE;
 
@@ -169,7 +169,7 @@ function myphpnet_showug($enable = null) {
 }
 
 // Save user settings in cookie
-function myphpnet_save()
+function myphpnet_save(): void
 {
     global $MYPHPNET;
 
@@ -183,7 +183,7 @@ function myphpnet_save()
 
 }
 
-function google_cse() {
+function google_cse(): void {
 ?>
 <noscript>
   php.net's search functionality requires JavaScript to operate. Please enable
diff --git a/include/results.inc b/include/results.inc
index 90c1864625..25f93bf64b 100644
--- a/include/results.inc
+++ b/include/results.inc
@@ -1,5 +1,5 @@
 <?php
-function search_results($res, $q, $profile = 'all', $per_page = 10, $s = 0, $l = 'en', $show_title = true, $show_foot = true, $show_attrib = true) {
+function search_results($res, $q, $profile = 'all', $per_page = 10, $s = 0, $l = 'en', $show_title = true, $show_foot = true, $show_attrib = true): void {
     $start_result = $s;
     $end_result = $s + $res['ResultSet']['totalResultsReturned'] - 1;
 
diff --git a/include/shared-manual.inc b/include/shared-manual.inc
index f17379bb3f..b25a9bd39e 100644
--- a/include/shared-manual.inc
+++ b/include/shared-manual.inc
@@ -112,7 +112,7 @@ function manual_notes_load(string $id): array
 }
 
 // Print out one user note entry
-function manual_note_display(UserNote $note, $voteOption = true)
+function manual_note_display(UserNote $note, $voteOption = true): void
 {
     if ($note->user) {
         $name = "\n  <strong class=\"user\"><em>" . htmlspecialchars($note->user) . "</em></strong>";
@@ -264,7 +264,7 @@ function manual_navigation_methodname($methodname) {
 
 // Set up variables important for this page
 // including HTTP header information
-function manual_setup($setup) {
+function manual_setup($setup): void {
     global $PGI, $MYSITE, $USERNOTES;
     global $ACTIVE_ONLINE_LANGUAGES;
 
@@ -381,7 +381,7 @@ CHANGE_LANG;
     return trim($r);
 }
 
-function manual_footer() {
+function manual_footer(): void {
     global $USERNOTES, $__RELATED;
 
     manual_notes($USERNOTES);
diff --git a/include/site.inc b/include/site.inc
index 65183ed1de..d0426b9f20 100644
--- a/include/site.inc
+++ b/include/site.inc
@@ -123,7 +123,7 @@ function mirror_type($site = false)
 }
 
 // Redirect to an URI on this mirror site or outside this site
-function mirror_redirect($absoluteURI)
+function mirror_redirect($absoluteURI): void
 {
     global $MYSITE;
 
@@ -160,7 +160,7 @@ function mirror_setcookie($name, $content, $exptime)
 
 // Use this function to write out proper headers on
 // pages where the content should not be publicly cached
-function header_nocache()
+function header_nocache(): void
 {
     // Only try to send out headers in case
     // those were not sent already