diff --git a/controllers/bookmark.php b/controllers/bookmark.php
index f36456e..ba184e1 100644
--- a/controllers/bookmark.php
+++ b/controllers/bookmark.php
@@ -38,7 +38,7 @@ Router\get_action('bookmarks', function () {
     $group_id = Request\int_param('group_id', null);
     $feed_ids = array();
 
-    if (! is_null($group_id)) {
+    if ($group_id !== null) {
         $feed_ids = Model\Group\get_feeds_by_group($group_id);
     }
 
diff --git a/controllers/common.php b/controllers/common.php
index 8af9551..0384e54 100644
--- a/controllers/common.php
+++ b/controllers/common.php
@@ -7,7 +7,7 @@ Router\before(function ($action) {
     // Select the requested database either from post param database or from the
     // session variable. If it fails, logout to destroy session and
     // 'remember me' cookie
-    if (! is_null(Request\value('database')) && ! Model\Database\select(Request\value('database'))) {
+    if (Request\value('database') !== null && ! Model\Database\select(Request\value('database'))) {
         Model\User\logout();
         Response\redirect('?action=login');
     } elseif (! empty($_SESSION['database'])) {
diff --git a/controllers/history.php b/controllers/history.php
index 3849cb7..aa6d167 100644
--- a/controllers/history.php
+++ b/controllers/history.php
@@ -8,7 +8,7 @@ Router\get_action('history', function () {
     $group_id = Request\int_param('group_id', null);
     $feed_ids = array();
     
-    if (! is_null($group_id)) {
+    if ($group_id !== null) {
         $feed_ids = Model\Group\get_feeds_by_group($group_id);
     }
 
@@ -59,7 +59,7 @@ Router\get_action('confirm-flush-history', function () {
 Router\get_action('flush-history', function () {
     $group_id = Request\int_param('group_id', null);
     
-    if (!is_null($group_id)) {
+    if ($group_id !== null) {
         Model\Item\mark_group_as_removed($group_id);
     } else {
         Model\Item\mark_all_as_removed();
diff --git a/controllers/item.php b/controllers/item.php
index 46cf3f3..dfc2108 100644
--- a/controllers/item.php
+++ b/controllers/item.php
@@ -11,7 +11,7 @@ Router\get_action('unread', function () {
     $group_id = Request\int_param('group_id', null);
     $feed_ids = array();
 
-    if (! is_null($group_id)) {
+    if ($group_id !== null) {
         $feed_ids = Model\Group\get_feeds_by_group($group_id);
     }
 
@@ -160,7 +160,7 @@ Router\post_action('mark-item-unread', function () {
 Router\get_action('mark-all-read', function () {
     $group_id = Request\int_param('group_id', null);
 
-    if (!is_null($group_id)) {
+    if ($group_id !== null) {
         Model\Item\mark_group_as_read($group_id);
     } else {
         Model\Item\mark_all_as_read();
diff --git a/fever/index.php b/fever/index.php
index fedc801..dedfe90 100644
--- a/fever/index.php
+++ b/fever/index.php
@@ -309,7 +309,7 @@ foreach (array_keys($_GET) as $action) {
 }
 
 if (! empty($_POST['mark']) && ! empty($_POST['as'])
-    && ! is_null(filter_input(INPUT_POST, 'id', FILTER_VALIDATE_INT, array('options' => array('default' => null, 'min_range' => -1))))) {
+    && filter_input(INPUT_POST, 'id', FILTER_VALIDATE_INT, array('options' => array('default' => null, 'min_range' => -1))) !== null) {
     if ($_POST['mark'] === 'item') {
         route('write_items');
     } elseif ($_POST['mark'] === 'feed' && ! empty($_POST['before'])) {
diff --git a/lib/Translator.php b/lib/Translator.php
index 3024856..1b943b9 100644
--- a/lib/Translator.php
+++ b/lib/Translator.php
@@ -109,7 +109,7 @@ namespace Translator {
             }
         }
 
-        for ($i = $plural; $i >= 0; $i--) {
+        for ($i = $plural; $i >= 0; --$i) {
             if (isset($locales[$identifier][$i])) {
                 return $locales[$identifier][$i];
             }
diff --git a/lib/helpers.php b/lib/helpers.php
index a741472..ee8231b 100644
--- a/lib/helpers.php
+++ b/lib/helpers.php
@@ -17,7 +17,7 @@ function parse_app_version($refnames, $commithash)
     if ($refnames !== '$Format:%d$') {
         $tag = preg_replace('/\s*\(.*tag:\sv([^,]+).*\)/i', '\1', $refnames);
 
-        if (!is_null($tag) && $tag !== $refnames) {
+        if ($tag !== null && $tag !== $refnames) {
             return $tag;
         }
     }
@@ -222,7 +222,7 @@ function form_hidden($name, $values = array())
 
 function form_default_select($name, array $options, $values = array(), array $errors = array(), $class = '')
 {
-    $options = array('' => '?') + $options;
+    $options += array('' => '?');
     return form_select($name, $options, $values, $errors, $class);
 }
 
diff --git a/lib/password.php b/lib/password.php
index d4972ab..a2d9530 100644
--- a/lib/password.php
+++ b/lib/password.php
@@ -114,9 +114,9 @@ if (!defined('PASSWORD_BCRYPT')) {
             }
             if (!$buffer_valid || strlen($buffer) < $raw_length) {
                 $bl = strlen($buffer);
-                for ($i = 0; $i < $raw_length; $i++) {
+                for ($i = 0; $i < $raw_length; ++$i) {
                     if ($i < $bl) {
-                        $buffer[$i] = $buffer[$i] ^ chr(mt_rand(0, 255));
+                        $buffer[$i] ^= chr(mt_rand(0, 255));
                     } else {
                         $buffer .= chr(mt_rand(0, 255));
                     }
@@ -212,12 +212,13 @@ if (!defined('PASSWORD_BCRYPT')) {
             return false;
         }
         $ret = crypt($password, $hash);
-        if (!is_string($ret) || strlen($ret) != strlen($hash) || strlen($ret) <= 13) {
+        $len = strlen($ret);
+        if (!is_string($ret) || $len != strlen($hash) || $len <= 13) {
             return false;
         }
 
         $status = 0;
-        for ($i = 0; $i < strlen($ret); $i++) {
+        for ($i = 0; $i < $len; ++$i) {
             $status |= (ord($ret[$i]) ^ ord($hash[$i]));
         }
 
diff --git a/models/item.php b/models/item.php
index c043cdf..8ba36b6 100644
--- a/models/item.php
+++ b/models/item.php
@@ -244,7 +244,7 @@ function get_nav($item, $status = array('unread'), $bookmark = array(1, 0), $fee
     $next_item = null;
     $previous_item = null;
 
-    for ($i = 0, $ilen = count($items); $i < $ilen; $i++) {
+    for ($i = 0, $ilen = count($items); $i < $ilen; ++$i) {
         if ($items[$i]['id'] == $item['id']) {
             if ($i > 0) {
                 $j = $i - 1;
@@ -255,7 +255,7 @@ function get_nav($item, $status = array('unread'), $bookmark = array(1, 0), $fee
                         break;
                     }
 
-                    $j--;
+                    --$j;
                 }
             }
 
@@ -268,7 +268,7 @@ function get_nav($item, $status = array('unread'), $bookmark = array(1, 0), $fee
                         break;
                     }
 
-                    $j++;
+                    ++$j;
                 }
             }
 
diff --git a/scripts/sync-locales.php b/scripts/sync-locales.php
index f36fc70..f3169e3 100755
--- a/scripts/sync-locales.php
+++ b/scripts/sync-locales.php
@@ -49,7 +49,7 @@ foreach (new DirectoryIterator('locales') as $fileInfo) {
 
         $filename = 'locales/'.$fileInfo->getFilename().'/translations.php';
 
-        echo $fileInfo->getFilename().' ('.$filename.')'.PHP_EOL;
+        echo $fileInfo->getFilename(), ' (', $filename, ')', PHP_EOL;
 
         file_put_contents($filename, update_missing_locales($reference, $filename));
     }
diff --git a/templates/about.php b/templates/about.php
index 5ce74da..bd5707a 100644
--- a/templates/about.php
+++ b/templates/about.php
@@ -16,7 +16,7 @@
         <h3><?= t('Bookmarks') ?></h3>
         <ul>
             <li>
-                <a href="<?= Helper\get_current_base_url().'?action=bookmark-feed&amp;database='.urlencode($db_name).'&amp;token='.urlencode($config['feed_token']) ?>" target="_blank"><?= t('Bookmark RSS Feed') ?></a>
+                <a href="<?= Helper\get_current_base_url(), '?action=bookmark-feed&amp;database=', urlencode($db_name), '&amp;token=', urlencode($config['feed_token']) ?>" target="_blank"><?= t('Bookmark RSS Feed') ?></a>
             </li>
         </ul>
     </div>
diff --git a/templates/api.php b/templates/api.php
index e5dd7d6..34a68c1 100644
--- a/templates/api.php
+++ b/templates/api.php
@@ -15,7 +15,7 @@
     <div class="panel panel-default">
         <h3 id="fever"><?= t('Fever API') ?></h3>
         <ul>
-            <li><?= t('API endpoint:') ?> <strong><?= Helper\get_current_base_url().'fever/' ?></strong></li>
+            <li><?= t('API endpoint:') ?> <strong><?= Helper\get_current_base_url(), 'fever/' ?></strong></li>
             <li><?= t('API username:') ?> <strong><?= Helper\escape($config['username']) ?></strong></li>
             <li><?= t('API token:') ?> <strong><?= Helper\escape($config['fever_token']) ?></strong></li>
         </ul>
@@ -23,7 +23,7 @@
     <div class="panel panel-default">
         <h3 id="api"><?= t('Miniflux API') ?></h3>
         <ul>
-            <li><?= t('API endpoint:') ?> <strong><?= Helper\get_current_base_url().'jsonrpc.php' ?></strong></li>
+            <li><?= t('API endpoint:') ?> <strong><?= Helper\get_current_base_url(), 'jsonrpc.php' ?></strong></li>
             <li><?= t('API username:') ?> <strong><?= Helper\escape($config['username']) ?></strong></li>
             <li><?= t('API token:') ?> <strong><?= Helper\escape($config['api_token']) ?></strong></li>
         </ul>
diff --git a/templates/bookmarks.php b/templates/bookmarks.php
index 364e919..43e1bb8 100644
--- a/templates/bookmarks.php
+++ b/templates/bookmarks.php
@@ -1,4 +1,4 @@
-<?php if (empty($items) && is_null($group_id)): ?>
+<?php if (empty($items) && $group_id === null): ?>
     <p class="alert alert-info"><?= t('No bookmark') ?></p>
 <?php else: ?>
 
diff --git a/templates/confirm_flush_items.php b/templates/confirm_flush_items.php
index c554bba..f165989 100644
--- a/templates/confirm_flush_items.php
+++ b/templates/confirm_flush_items.php
@@ -5,6 +5,6 @@
 <p class="alert alert-info"><?= t('Do you really want to remove these items from your history?') ?></p>
 
 <div class="form-actions">
-    <a href="?action=flush-history<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>" class="btn btn-red"><?= t('Remove') ?></a>
-    <?= t('or') ?> <a href="?action=history<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>"><?= t('cancel') ?></a>
+    <a href="?action=flush-history<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>" class="btn btn-red"><?= t('Remove') ?></a>
+    <?= t('or') ?> <a href="?action=history<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>"><?= t('cancel') ?></a>
 </div>
\ No newline at end of file
diff --git a/templates/feeds.php b/templates/feeds.php
index 417f68e..0a60528 100644
--- a/templates/feeds.php
+++ b/templates/feeds.php
@@ -34,7 +34,7 @@
                 <?= Helper\favicon($favicons, $feed['id']) ?>
 
                 <a href="?action=feed-items&amp;feed_id=<?= $feed['id'] ?>" title="<?= t('Show only this subscription') ?>"><?= Helper\escape($feed['title']) ?></a>
-                &lrm;<span class="items-count"><?= $feed['items_unread'] .'/' . $feed['items_total'] ?></span>
+                &lrm;<span class="items-count"><?= $feed['items_unread'], '/', $feed['items_total'] ?></span>
 
                 <?php if ($feed['enabled']): ?>
 
@@ -42,7 +42,7 @@
 
                     <?php if ($feed['last_checked']): ?>
                         <time class="feed-last-checked" data-after-update="<?= t('updated just now') ?>">
-                            <?= t('checked at').' '.dt('%e %B %Y %k:%M', $feed['last_checked']) ?>
+                            <?= t('checked at'), ' ', dt('%e %B %Y %k:%M', $feed['last_checked']) ?>
                         </time>
                     <?php else: ?>
                         <span class="feed-last-checked" data-after-update="<?= t('updated just now') ?>">
diff --git a/templates/history.php b/templates/history.php
index 1e509c1..db748ff 100644
--- a/templates/history.php
+++ b/templates/history.php
@@ -18,9 +18,9 @@
 
         <ul>
             <li>
-                <a href="?action=history<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>&amp;order=updated&amp;direction=<?= $direction == 'asc' ? 'desc' : 'asc' ?>"><?= tne('sort by date %s(%s)%s', '<span class="hide-mobile">', $direction == 'desc' ? t('older first') : t('most recent first'), '</span>') ?></a>
+                <a href="?action=history<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>&amp;order=updated&amp;direction=<?= $direction == 'asc' ? 'desc' : 'asc' ?>"><?= tne('sort by date %s(%s)%s', '<span class="hide-mobile">', $direction == 'desc' ? t('older first') : t('most recent first'), '</span>') ?></a>
             </li>
-            <li><a href="?action=confirm-flush-history<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>"><?= t('flush all items') ?></a></li>
+            <li><a href="?action=confirm-flush-history<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>"><?= t('flush all items') ?></a></li>
         </ul>
     </div>
 
diff --git a/templates/unread_items.php b/templates/unread_items.php
index 36803e4..8e7aab7 100644
--- a/templates/unread_items.php
+++ b/templates/unread_items.php
@@ -16,10 +16,10 @@
 
         <ul>
             <li>
-                <a href="?action=unread<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>&amp;order=updated&amp;direction=<?= $direction == 'asc' ? 'desc' : 'asc' ?>"><?= tne('sort by date %s(%s)%s', '<span class="hide-mobile">',$direction == 'desc' ? t('older first') : t('most recent first'), '</span>') ?></a>
+                <a href="?action=unread<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>&amp;order=updated&amp;direction=<?= $direction == 'asc' ? 'desc' : 'asc' ?>"><?= tne('sort by date %s(%s)%s', '<span class="hide-mobile">',$direction == 'desc' ? t('older first') : t('most recent first'), '</span>') ?></a>
             </li>
             <li>
-                <a href="?action=mark-all-read<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>"><?= t('mark all as read') ?></a>
+                <a href="?action=mark-all-read<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>"><?= t('mark all as read') ?></a>
             </li>
         </ul>
     </div>
@@ -43,7 +43,7 @@
             <?php endforeach ?>
 
             <div id="bottom-menu">
-                <a href="?action=mark-all-read<?= is_null($group_id) ? '' : '&amp;group_id='.$group_id ?>"><?= t('mark all as read') ?></a>
+                <a href="?action=mark-all-read<?= $group_id === null ? '' : '&amp;group_id='.$group_id ?>"><?= t('mark all as read') ?></a>
             </div>
 
             <?= \Template\load('paging', array('menu' => $menu, 'nb_items' => $nb_items, 'items_per_page' => $items_per_page, 'offset' => $offset, 'order' => $order, 'direction' => $direction, 'group_id' => $group_id)) ?>
diff --git a/tests/integration/minifluxTestCase.php b/tests/integration/minifluxTestCase.php
index 68d40ba..27eb77f 100644
--- a/tests/integration/minifluxTestCase.php
+++ b/tests/integration/minifluxTestCase.php
@@ -108,7 +108,7 @@ abstract class minifluxTestCase extends PHPUnit_Extensions_Selenium2TestCase
 
     protected function getConnection()
     {
-        if (is_null(static::$databaseConnection)) {
+        if (static::$databaseConnection === null) {
             // let Miniflux setup the database
             require_once dirname(__FILE__).DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'common.php';
 
@@ -142,7 +142,7 @@ abstract class minifluxTestCase extends PHPUnit_Extensions_Selenium2TestCase
 
     protected function getDatabaseTester($dataset)
     {
-        if (is_null(static::$databaseTester)) {
+        if (static::$databaseTester === null) {
             $rdataset = new PHPUnit_Extensions_Database_DataSet_ReplacementDataSet($dataset);
             $rdataset->addSubStrReplacement('##TIMESTAMP##', substr((string)(time()-100), 0, -2));
 
@@ -247,7 +247,7 @@ abstract class minifluxTestCase extends PHPUnit_Extensions_Selenium2TestCase
                     $elements = $this->elements($this->using('id')->value($id));
 
                     if (count($elements) === 1 && $elements[0]->text() == $text
-                        || count($elements) === 0 && is_null($text)) {
+                        || count($elements) === 0 && $text === null) {
                         return true;
                     }
                 } catch (PHPUnit_Extensions_Selenium2TestCase_WebDriverException $e) {
diff --git a/worker.php b/worker.php
index b1f2802..644a504 100644
--- a/worker.php
+++ b/worker.php
@@ -19,10 +19,10 @@ function check_job_left(Pheanstalk $connection, array $options)
 
         if (in_array(BEANSTALKD_QUEUE, $queues)) {
             $stats = $connection->statsTube(BEANSTALKD_QUEUE);
-            echo 'Jobs in queue: '.$stats->current_jobs_ready.PHP_EOL;
+            echo 'Jobs in queue: ', $stats->current_jobs_ready, PHP_EOL;
             (int) $stats->current_jobs_ready === 0 && exit(0);
         } else {
-            echo 'No queue'.PHP_EOL;
+            echo 'No queue', PHP_EOL;
             exit(0);
         }
     }
@@ -35,7 +35,7 @@ check_job_left($connection, $options);
 while ($job = $connection->reserveFromTube(BEANSTALKD_QUEUE)) {
     $feed_id = $job->getData();
 
-    echo 'Processing feed_id='.$feed_id.PHP_EOL;
+    echo 'Processing feed_id=', $feed_id, PHP_EOL;
 
     Model\Feed\refresh($feed_id);
     $connection->delete($job);