diff --git a/dl_list.php b/dl_list.php
index 49fdf830a..040bbf0a3 100644
--- a/dl_list.php
+++ b/dl_list.php
@@ -39,10 +39,10 @@ if ($mode == 'set_dl_status' || $mode == 'set_topics_dl_status') {
 $full_url = isset($_POST['full_url']) ? str_replace('&', '&', htmlspecialchars($_POST['full_url'])) : '';
 
 if (isset($_POST['redirect_type']) && $_POST['redirect_type'] == 'search') {
-    $redirect_type = "search.php";
+    $redirect_type = 'search.php';
     $redirect = $full_url ?: "$dl_key=1";
 } else {
-    $redirect_type = (!$topic_id) ? "viewforum.php" : "viewtopic.php";
+    $redirect_type = (!$topic_id) ? 'viewforum.php' : 'viewtopic.php';
     $redirect = $full_url ?: ((!$topic_id) ? POST_FORUM_URL . "=$forum_id" : POST_TOPIC_URL . "=$topic_id");
 }
 
@@ -136,4 +136,4 @@ if ($topics_ary && ($mode == 'set_dl_status' || $mode == 'set_topics_dl_status')
     redirect("$redirect_type?$redirect");
 }
 
-redirect("index.php");
+redirect('index.php');
diff --git a/library/includes/page_header.php b/library/includes/page_header.php
index 585d7fdc1..37b3ca143 100644
--- a/library/includes/page_header.php
+++ b/library/includes/page_header.php
@@ -124,7 +124,7 @@ $template->assign_vars([
     'USE_TABLESORTER' => !empty($page_cfg['use_tablesorter']),
 
     'SITENAME' => $bb_cfg['sitename'],
-    'U_INDEX' => BB_ROOT . "index.php",
+    'U_INDEX' => BB_ROOT . 'index.php',
     'T_INDEX' => sprintf($lang['FORUM_INDEX'], $bb_cfg['sitename']),
 
     'IS_GUEST' => IS_GUEST,
diff --git a/library/includes/ucp/email.php b/library/includes/ucp/email.php
index 66f986a51..c5e4f16df 100644
--- a/library/includes/ucp/email.php
+++ b/library/includes/ucp/email.php
@@ -13,7 +13,7 @@ if (!defined('BB_ROOT')) {
 
 // Is send through board enabled? No, return to index
 if (!$bb_cfg['board_email_form']) {
-    redirect("index.php");
+    redirect('index.php');
 }
 
 set_die_append_msg();
diff --git a/login.php b/login.php
index 7fc75cacd..5dc20198e 100644
--- a/login.php
+++ b/login.php
@@ -22,10 +22,10 @@ if (!empty($_GET['logout'])) {
     if (!IS_GUEST) {
         $user->session_end();
     }
-    redirect("index.php");
+    redirect('index.php');
 }
 
-$redirect_url = "index.php";
+$redirect_url = 'index.php';
 $login_errors = [];
 
 // Requested redirect
@@ -38,13 +38,13 @@ if (preg_match('/^redirect=([a-z0-9\.#\/\?&=\+\-_]+)/si', $_SERVER['QUERY_STRING
 } elseif (!empty($_POST['redirect'])) {
     $redirect_url = str_replace('&', '&', htmlspecialchars($_POST['redirect']));
 } elseif (!empty($_SERVER['HTTP_REFERER']) && ($parts = @parse_url($_SERVER['HTTP_REFERER']))) {
-    $redirect_url = ($parts['path'] ?? "index.php") . (isset($parts['query']) ? '?' . $parts['query'] : '');
+    $redirect_url = ($parts['path'] ?? 'index.php') . (isset($parts['query']) ? '?' . $parts['query'] : '');
 }
 
 $redirect_url = str_replace(['&admin=1', '?admin=1'], '', $redirect_url);
 
 if (!$redirect_url || false !== strpos(urldecode($redirect_url), "\n") || false !== strpos(urldecode($redirect_url), "\r") || false !== strpos(urldecode($redirect_url), ';url')) {
-    $redirect_url = "index.php";
+    $redirect_url = 'index.php';
 }
 
 $redirect_url = str_replace("&sid={$user->data['session_id']}", '', $redirect_url);
diff --git a/memberlist.php b/memberlist.php
index 7cbe8f58f..939535146 100644
--- a/memberlist.php
+++ b/memberlist.php
@@ -69,7 +69,7 @@ $select_sort_order .= '</select>';
 $template->assign_vars([
     'S_MODE_SELECT' => $select_sort_mode,
     'S_ORDER_SELECT' => $select_sort_order,
-    'S_MODE_ACTION' => "memberlist.php",
+    'S_MODE_ACTION' => 'memberlist.php',
     'S_USERNAME' => $paginationusername,
 ]);
 
diff --git a/search.php b/search.php
index 78ffac698..2f6c6d7e0 100644
--- a/search.php
+++ b/search.php
@@ -288,7 +288,7 @@ if (empty($_GET) && empty($_POST)) {
 
         'THIS_USER_ID' => $userdata['user_id'],
         'THIS_USER_NAME' => addslashes($userdata['username']),
-        'SEARCH_ACTION' => "search.php",
+        'SEARCH_ACTION' => 'search.php',
         'U_SEARCH_USER' => "search.php?mode=searchuser&amp;input_name=$poster_name_key",
         'ONLOAD_FOCUS_ID' => 'text_match_input',