diff --git a/activity_hub.php b/activity_hub.php
index 511cbfc1c..c396eb123 100644
--- a/activity_hub.php
+++ b/activity_hub.php
@@ -245,7 +245,7 @@ function progress_snapshot_table($show_filtered_projects, $show_filtering_links,
 
     // Stage rows
     foreach (Stages::get_all() as $stage) {
-        if (is_a($stage, 'Pool') || is_a($stage, 'Round')) {
+        if ($stage instanceof Pool || $stage instanceof Round) {
             continue;
         }
         if ($stage->id == "SR") {
@@ -324,7 +324,7 @@ function summarize_stage($stage, $desired_states, $show_filtered_projects = fals
     }
 
     // If we're a round, get page information and calculate status.
-    if (is_a($stage, 'Round')) {
+    if ($stage instanceof Round) {
         $round_stats = get_site_page_tally_summary($stage->id);
 
         [$progress_bar_width, $progress_bar_class, $percent_complete] =
@@ -431,7 +431,7 @@ function summarize_stage($stage, $desired_states, $show_filtered_projects = fals
     echo "</td>";
 
     // Rounds and Pools also get project totals.
-    if (is_a($stage, 'Round') || is_a($stage, 'Pool')) {
+    if ($stage instanceof Round || $stage instanceof Pool) {
         echo "<td>$total_projects</td>";
         foreach ($desired_states as $desired_state) {
             echo "<td>";
@@ -449,7 +449,7 @@ function summarize_stage($stage, $desired_states, $show_filtered_projects = fals
     }
 
     // Rounds also get page totals.
-    if (is_a($stage, 'Round')) {
+    if ($stage instanceof Round) {
         echo "<td class='pages-goal'>{$round_stats->curr_day_goal}</td>";
         echo "<td class='pages-completed'>{$round_stats->curr_day_actual}</td>";
         echo "<td><div class='progressbar $progress_bar_class' style='width: $progress_bar_width%;'>&nbsp;</div><p style='clear: both; margin: 0;'>$percent_complete%</p></td>";
@@ -470,7 +470,7 @@ function summarize_stage($stage, $desired_states, $show_filtered_projects = fals
         // specificity of inline style is needed to override default style to
         // force the filter links to align to the left.
         echo "<tr>";
-        if (is_a($stage, 'Round')) {
+        if ($stage instanceof Round) {
             echo "<td colspan='7' style='text-align: left;'>";
         } else {
             echo "<td colspan='3' style='text-align: left;'>";
diff --git a/pinc/Activity.inc b/pinc/Activity.inc
index 1c437ed16..404e17813 100644
--- a/pinc/Activity.inc
+++ b/pinc/Activity.inc
@@ -208,7 +208,7 @@ class Activity
         // which seems worse.
         // TODO: We should probably have a function for declaring criteria.
         global $ACCESS_CRITERIA;
-        if (is_a($this, 'Round')) {
+        if ($this instanceof Round) {
             $ACCESS_CRITERIA[$this->id] =
                 sprintf(_("'%s' pages completed"), $this->id);
         }
diff --git a/pinc/showavailablebooks.inc b/pinc/showavailablebooks.inc
index c1338d577..4cd22853a 100644
--- a/pinc/showavailablebooks.inc
+++ b/pinc/showavailablebooks.inc
@@ -427,7 +427,7 @@ function show_project_listing(
     // $presort allows us to place certain projects at the top of all project
     // listings such as BEGIN projects, but only for Rounds.
     $presort = "";
-    if (is_a($stage, 'Round')) {
+    if ($stage instanceof Round) {
         $presort = round_project_listing_presort($stage);
         if (!empty($presort)) {
             $presort .= ',';
@@ -521,7 +521,7 @@ function show_project_listing(
             } elseif ($col_id == "genre") {
                 $genre = $book['trans_genre'];
                 if ($book['difficulty'] == "beginner") {
-                    if (is_a($stage, 'Round')) {
+                    if ($stage instanceof Round) {
                         if ($stage->is_a_mentee_round()) {
                             $genre = _("BEGINNERS ONLY")." ".$genre;
                         } elseif ($stage->is_a_mentor_round()) {