diff --git a/CHANGELOG.md b/CHANGELOG.md
index b05cefc5..fc4ab48a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+* now requires PHP 5.4.0+
+* lots of code cleanup and refactorings
+* changes API
 * fixes some styles in IE10
 * resets IE edge mode
 * fixes preview bottom bar for small screen widths
diff --git a/src/_h5ai/server/php/inc/class-api.php b/src/_h5ai/server/php/inc/class-api.php
index fc391206..0dc3ae37 100644
--- a/src/_h5ai/server/php/inc/class-api.php
+++ b/src/_h5ai/server/php/inc/class-api.php
@@ -14,7 +14,7 @@ class Api {
     public function apply() {
 
         $action = Util::get_request_param("action");
-        $supported = array("login", "logout", "get", "download");
+        $supported = ["login", "logout", "get", "download"];
         Util::json_fail(Util::ERR_UNSUPPORTED, "unsupported action", !in_array($action, $supported));
 
         $methodname = "on_${action}";
@@ -26,22 +26,22 @@ class Api {
 
         $pass = Util::get_request_param("pass");
         $_SESSION[AS_ADMIN_SESSION_KEY] = sha1($pass) === PASSHASH;
-        Util::json_exit(array("asAdmin" => $_SESSION[AS_ADMIN_SESSION_KEY]));
+        Util::json_exit(["asAdmin" => $_SESSION[AS_ADMIN_SESSION_KEY]]);
     }
 
 
     private function on_logout() {
 
         $_SESSION[AS_ADMIN_SESSION_KEY] = false;
-        Util::json_exit(array("asAdmin" => $_SESSION[AS_ADMIN_SESSION_KEY]));
+        Util::json_exit(["asAdmin" => $_SESSION[AS_ADMIN_SESSION_KEY]]);
     }
 
 
     private function on_get() {
 
-        $response = array();
+        $response = [];
 
-        foreach (array("setup", "options", "types", "theme", "langs") as $name) {
+        foreach (["setup", "options", "types", "theme", "langs"] as $name) {
             if (Util::get_boolean_request_param($name, false)) {
 
                 $methodname = "get_${name}";
diff --git a/src/_h5ai/server/php/inc/class-app.php b/src/_h5ai/server/php/inc/class-app.php
index 949a7417..fd0b3a1d 100644
--- a/src/_h5ai/server/php/inc/class-app.php
+++ b/src/_h5ai/server/php/inc/class-app.php
@@ -3,8 +3,8 @@
 class App {
 
     private static $RE_DELIMITER = "|";
-    private static $ICON_EXTS = array("svg", "png", "jpg");
-    private static $CUSTOM_EXTS = array("html", "md");
+    private static $ICON_EXTS = ["svg", "png", "jpg"];
+    private static $CUSTOM_EXTS = ["html", "md"];
 
 
     private $options;
@@ -30,17 +30,17 @@ class App {
 
     public function get_setup() {
 
-        $keys = array(
+        $keys = [
             "APP_HREF",
             "ROOT_HREF",
             "VERSION",
 
             "AS_ADMIN",
             "HAS_CUSTOM_PASSHASH"
-        );
+        ];
 
         if (AS_ADMIN) {
-            $keys = array_merge($keys, array(
+            $keys = array_merge($keys, [
                 "PHP_VERSION",
                 "MIN_PHP_VERSION",
                 "HAS_MIN_PHP_VERSION",
@@ -61,10 +61,10 @@ class App {
                 "HAS_CMD_FFMPEG",
                 "HAS_CMD_AVCONV",
                 "HAS_CMD_DU"
-            ));
+            ]);
         }
 
-        $setup = array();
+        $setup = [];
         foreach ($keys as $key) {
             $setup[$key] = constant($key);
         }
@@ -83,7 +83,7 @@ class App {
         $theme = $this->get_option("view.theme", "-NONE-");
         $theme_path = APP_PATH . "/client/images/themes/${theme}";
 
-        $icons = array();
+        $icons = [];
 
         if (is_dir($theme_path)) {
             if ($dir = opendir($theme_path)) {
@@ -105,7 +105,7 @@ class App {
 
         $rel_path = substr($path, strlen(ROOT_PATH));
         $parts = explode("/", $rel_path);
-        $encoded_parts = array();
+        $encoded_parts = [];
         foreach ($parts as $part) {
             if ($part != "") {
                 $encoded_parts[] = rawurlencode($part);
@@ -130,7 +130,7 @@ class App {
             return true;
         }
 
-        foreach ($this->get_option("view.hidden", array()) as $re) {
+        foreach ($this->get_option("view.hidden", []) as $re) {
             $re = App::$RE_DELIMITER . str_replace(App::$RE_DELIMITER, '\\' . App::$RE_DELIMITER, $re) . App::$RE_DELIMITER;
             if (preg_match($re, $name)) {
                 return true;
@@ -143,7 +143,7 @@ class App {
 
     public function read_dir($path) {
 
-        $names = array();
+        $names = [];
         if (is_dir($path)) {
             foreach (scandir($path) as $name) {
                 if (
@@ -176,7 +176,7 @@ class App {
             return false;
         }
 
-        foreach ($this->get_option("view.unmanaged", array()) as $name) {
+        foreach ($this->get_option("view.unmanaged", []) as $name) {
             if (file_exists($path . "/" . $name)) {
                 return false;
             }
@@ -199,10 +199,10 @@ class App {
     public function get_items($href, $what) {
 
         if (!$this->is_managed_href($href)) {
-            return array();
+            return [];
         }
 
-        $cache = array();
+        $cache = [];
         $folder = Item::get($this, $this->to_path($href), $cache);
 
         // add content of subfolders
@@ -219,8 +219,8 @@ class App {
             $folder = $folder->get_parent($cache);
         }
 
-        uasort($cache, array("Item", "cmp"));
-        $result = array();
+        uasort($cache, ["Item", "cmp"]);
+        $result = [];
         foreach ($cache as $p => $item) {
             $result[] = $item->to_json_object();
         }
@@ -249,10 +249,10 @@ class App {
             $path = $this->get_current_path();
         }
 
-        $cache = array();
+        $cache = [];
         $folder = Item::get($this, $path, $cache);
         $items = $folder->get_content($cache);
-        uasort($items, array("Item", "cmp"));
+        uasort($items, ["Item", "cmp"]);
 
         $html = "<table>";
 
@@ -291,7 +291,7 @@ class App {
 
     public function get_langs() {
 
-        $langs = array();
+        $langs = [];
         $l10n_path = APP_PATH . "/conf/l10n";
         if (is_dir($l10n_path)) {
             if ($dir = opendir($l10n_path)) {
@@ -311,7 +311,7 @@ class App {
 
     public function get_l10n($iso_codes) {
 
-        $results = array();
+        $results = [];
 
         foreach ($iso_codes as $iso_code) {
             $file = APP_PATH . "/conf/l10n/" . $iso_code . ".json";
@@ -339,10 +339,10 @@ class App {
     public function get_customizations($href) {
 
         if (!$this->get_option("custom.enabled", false)) {
-            return array(
-                "header" => array("content" => null, "type" => null),
-                "footer" => array("content" => null, "type" => null)
-            );
+            return [
+                "header" => ["content" => null, "type" => null],
+                "footer" => ["content" => null, "type" => null]
+            ];
         }
 
         $path = $this->to_path($href);
@@ -374,10 +374,10 @@ class App {
             $path = $parent_path;
         }
 
-        return array(
-            "header" => array("content" => $header, "type" => $header_type),
-            "footer" => array("content" => $footer, "type" => $footer_type)
-        );
+        return [
+            "header" => ["content" => $header, "type" => $header_type],
+            "footer" => ["content" => $footer, "type" => $footer_type]
+        ];
     }
 
 
diff --git a/src/_h5ai/server/php/inc/class-archive.php b/src/_h5ai/server/php/inc/class-archive.php
index 77822e35..c710c947 100644
--- a/src/_h5ai/server/php/inc/class-archive.php
+++ b/src/_h5ai/server/php/inc/class-archive.php
@@ -22,8 +22,8 @@ class Archive {
             return 500;
         }
 
-        $this->dirs = array();
-        $this->files = array();
+        $this->dirs = [];
+        $this->files = [];
 
         $this->add_hrefs($hrefs);
 
@@ -67,7 +67,7 @@ class Archive {
 
     private function php_tar($dirs, $files) {
 
-        $filesizes = array();
+        $filesizes = [];
         $total_size = 512 * count($dirs);
         foreach (array_keys($files) as $real_file) {
 
diff --git a/src/_h5ai/server/php/inc/class-bootstrap.php b/src/_h5ai/server/php/inc/class-bootstrap.php
index 9a85c037..dbc0341f 100644
--- a/src/_h5ai/server/php/inc/class-bootstrap.php
+++ b/src/_h5ai/server/php/inc/class-bootstrap.php
@@ -70,7 +70,7 @@ class Bootstrap {
         }
         define("SERVER_NAME", $server_name);
         define("SERVER_VERSION", $server_version);
-        define("HAS_SERVER", in_array($server_name, array("apache", "lighttpd", "nginx", "cherokee")));
+        define("HAS_SERVER", in_array($server_name, ["apache", "lighttpd", "nginx", "cherokee"]));
     }
 
 
@@ -118,7 +118,7 @@ class Bootstrap {
                 $cmd = "which";
             }
 
-            foreach (array("tar", "zip", "convert", "ffmpeg", "avconv", "du") as $c) {
+            foreach (["tar", "zip", "convert", "ffmpeg", "avconv", "du"] as $c) {
                 $cmds[$c] = ($cmd !== false) && Util::exec_0($cmd . " " . $c);
             }
 
diff --git a/src/_h5ai/server/php/inc/class-item.php b/src/_h5ai/server/php/inc/class-item.php
index 578487c4..79e13db7 100644
--- a/src/_h5ai/server/php/inc/class-item.php
+++ b/src/_h5ai/server/php/inc/class-item.php
@@ -54,11 +54,11 @@ class Item {
 
     public function to_json_object() {
 
-        $obj = array(
+        $obj = [
             "href" => $this->href,
             "time" => $this->date * 1000, // seconds (PHP) to milliseconds (JavaScript)
             "size" => $this->size
-        );
+        ];
 
         if ($this->is_folder) {
             $obj["managed"] = $this->app->is_managed_href($this->href);
@@ -81,7 +81,7 @@ class Item {
 
     public function get_content(&$cache) {
 
-        $items = array();
+        $items = [];
 
         if (!$this->app->is_managed_href($this->href)) {
             return $items;
diff --git a/src/_h5ai/server/php/inc/class-thumb.php b/src/_h5ai/server/php/inc/class-thumb.php
index e93c56ea..c04e03bc 100644
--- a/src/_h5ai/server/php/inc/class-thumb.php
+++ b/src/_h5ai/server/php/inc/class-thumb.php
@@ -2,9 +2,9 @@
 
 class Thumb {
 
-    private static $FFMPEG_CMDV = array("ffmpeg", "-ss", "0:00:10", "-i", "[SRC]", "-an", "-vframes", "1", "[DEST]");
-    private static $AVCONV_CMDV = array("avconv", "-ss", "0:00:10", "-i", "[SRC]", "-an", "-vframes", "1", "[DEST]");
-    private static $CONVERT_CMDV = array("convert", "-density", "200", "-quality", "100", "-sharpen", "0x1.0", "-strip", "[SRC][0]", "[DEST]");
+    private static $FFMPEG_CMDV = ["ffmpeg", "-ss", "0:00:10", "-i", "[SRC]", "-an", "-vframes", "1", "[DEST]"];
+    private static $AVCONV_CMDV = ["avconv", "-ss", "0:00:10", "-i", "[SRC]", "-an", "-vframes", "1", "[DEST]"];
+    private static $CONVERT_CMDV = ["convert", "-density", "200", "-quality", "100", "-sharpen", "0x1.0", "-strip", "[SRC][0]", "[DEST]"];
     private static $THUMB_CACHE = "thumbs";
 
 
@@ -240,7 +240,7 @@ class Image {
 
         $this->source = imagerotate($this->source, $angle, 0);
         if ( $angle === 90 || $angle === 270 ) {
-            list($this->width, $this->height) = array($this->height, $this->width);
+            list($this->width, $this->height) = [$this->height, $this->width];
         }
     }
 
diff --git a/src/_h5ai/server/php/inc/class-util.php b/src/_h5ai/server/php/inc/class-util.php
index cfa223b2..d91a4e57 100644
--- a/src/_h5ai/server/php/inc/class-util.php
+++ b/src/_h5ai/server/php/inc/class-util.php
@@ -16,7 +16,7 @@ class Util {
     }
 
 
-    public static function json_exit($obj = array()) {
+    public static function json_exit($obj = []) {
 
         header("Content-type: application/json;charset=utf-8");
         echo json_encode($obj);
@@ -27,7 +27,7 @@ class Util {
     public static function json_fail($err, $msg = "", $cond = true) {
 
         if ($cond) {
-            Util::json_exit(array("err" => $err, "msg" => $msg));
+            Util::json_exit(["err" => $err, "msg" => $msg]);
         }
     }
 
@@ -50,7 +50,6 @@ class Util {
 
     public static function is_post_request() {
 
-        // Logger::log("POSTED", $_POST);
         return (strtolower($_SERVER["REQUEST_METHOD"]) === "post");
     }
 
@@ -87,7 +86,7 @@ class Util {
     public static function load_commented_json($path) {
 
         if (!file_exists($path)) {
-            return array();
+            return [];
         }
 
         $content = file_get_contents($path);
@@ -121,7 +120,7 @@ class Util {
         }
         $cmd = implode(" ", array_map("escapeshellarg", $cmdv));
 
-        $lines = array();
+        $lines = [];
         $rc = null;
         exec($cmd, $lines, $rc);
         return implode("\n", $lines);
@@ -130,7 +129,7 @@ class Util {
 
     public static function exec_0($cmd) {
 
-        $lines = array();
+        $lines = [];
         $rc = null;
         try {
             @exec($cmd, $lines, $rc);
@@ -140,7 +139,7 @@ class Util {
     }
 
 
-    private static $size_cache = array();
+    private static $size_cache = [];
 
     public static function filesize($app, $path) {
 
@@ -184,7 +183,7 @@ class Util {
 
             if ($app->get_option("foldersize.enabled", false)) {
                 if (HAS_CMD_DU && $app->get_option("foldersize.type", null) === "shell-du") {
-                    $cmdv = array("du", "-sk", $path);
+                    $cmdv = ["du", "-sk", $path];
                     $size = intval(preg_replace("#\s.*$#", "", Util::exec_cmdv($cmdv)), 10) * 1024;
                 } else {
                     $size = 0;