diff --git a/cal.php b/cal.php
index ed02e43d0..3b5399959 100644
--- a/cal.php
+++ b/cal.php
@@ -230,7 +230,7 @@ function date_for_recur($recur, $day, $bom, $eom)
 }
 
 // Display a <div> for each of the events that are on a given day
-function display_events_for_day($day, $events)
+function display_events_for_day($day, $events): void
 {
     // For preservation of state in the links
     global $cm, $cy, $COUNTRY;
diff --git a/download-logos.php b/download-logos.php
index 02158900a..85f59dd1c 100644
--- a/download-logos.php
+++ b/download-logos.php
@@ -13,13 +13,13 @@ $SIDEBAR_DATA = '
 site_header("Download Logos", array("current" => "downloads"));
 
 // Print recommended star cell
-function print_star()
+function print_star(): void
 {
     echo "<td class=\"star\"><span class=\"star\" title=\"recommended\">*</span></td>\n";
 }
 
 // Provide a random bgcolor setting for a cell
-function random_bgcolor($min, $max)
+function random_bgcolor($min, $max): void
 {
     echo "style=\"background-color: #" .
          sprintf('%02x%02x%02x', rand($min, $max)*51, rand($min, $max)*51, rand($min, $max)*51) .
diff --git a/images/logo.php b/images/logo.php
index 525efb7da..0c64158c5 100644
--- a/images/logo.php
+++ b/images/logo.php
@@ -53,7 +53,7 @@ function get_accepted_encodings() {
 }
 
 
-function serve_compressed_if_available($logo) {
+function serve_compressed_if_available($logo): void {
     $encodings = get_accepted_encodings();
     if (!empty($encodings)) {
         foreach ($encodings as $encoding) {
diff --git a/index.php b/index.php
index 34f7b2a30..352d5750e 100644
--- a/index.php
+++ b/index.php
@@ -1,5 +1,5 @@
 <?php // vim: et
-(function($uri) {
+(function($uri): void {
     // Special redirect cases not able to be captured in error.php
     $shortcuts = [
         '/?:'    => '/language.operators.comparison#language.operators.comparison.ternary',
diff --git a/mailing-lists.php b/mailing-lists.php
index a2a5232b8..e134096af 100644
--- a/mailing-lists.php
+++ b/mailing-lists.php
@@ -304,7 +304,7 @@ if (isset($_POST['action'])) {
   );
 
 // Print out a table for a given list array
-function output_lists_table($mailing_lists)
+function output_lists_table($mailing_lists): void
 {
     echo '<table cellpadding="5" border="0" class="standard mailing-lists">', "\n";
     foreach ($mailing_lists as $listinfo) {
diff --git a/quickref.php b/quickref.php
index da786b9ca..940165521 100644
--- a/quickref.php
+++ b/quickref.php
@@ -24,7 +24,7 @@ if (empty($notfound)) {
 
 // Print out the table of found (or all) functions. The HTML comments are
 // needed to support MyCroft search (Mozilla browser family and Sherlock for MacOSX)
-function quickref_table($functions, $sort = true)
+function quickref_table($functions, $sort = true): void
 {
     global $LANG;
 
diff --git a/releases/index.php b/releases/index.php
index 4f141f8f2..b2bf361e2 100644
--- a/releases/index.php
+++ b/releases/index.php
@@ -186,7 +186,7 @@ function mk_rel(int $major,
 				/* bool | array */ $announcement,
 				array $source,
 				array $windows,
-				bool $museum) {
+				bool $museum): void {
 	printf("<a id=\"%s\"></a>\n<h2>%1\$s</h2>\n<ul>\n <li>Released: %s</li>\n <li>Announcement: ",
 	       ($pos = strpos($ver, " ")) ? substr($ver, 0, $pos) : $ver,
 	       $date);
diff --git a/submit-event.php b/submit-event.php
index 055c694d6..adba380c1 100644
--- a/submit-event.php
+++ b/submit-event.php
@@ -265,7 +265,7 @@ if ($process && count($errors) === 0) {
 site_footer();
 
 // Display an option list with one selected
-function display_options($options, $current)
+function display_options($options, $current): void
 {
     foreach ($options as $k => $v) {
         echo '<option value="', $k, '"',
diff --git a/urlhowto.php b/urlhowto.php
index 196be2bec..0ea3c0329 100644
--- a/urlhowto.php
+++ b/urlhowto.php
@@ -25,7 +25,7 @@ $SIDEBAR_DATA='
 ';
 
 site_header("URL Howto", array("current" => "help"));
-function a($href) {
+function a($href): void {
     global $MYSITE;
 	echo '<a href="' . $MYSITE . $href . '">' . $MYSITE . $href . '</a>';
 }