diff --git a/lib/Data/Filesystem.php b/lib/Data/Filesystem.php
index 751980ab..7df9be13 100644
--- a/lib/Data/Filesystem.php
+++ b/lib/Data/Filesystem.php
@@ -370,10 +370,7 @@ class Filesystem extends AbstractData
         foreach ($files as $pasteid) {
             if ($this->exists($pasteid)) {
                 $data = $this->read($pasteid);
-                if (
-                    array_key_exists('expire_date', $data['meta']) &&
-                    $data['meta']['expire_date'] < $time
-                ) {
+                if (($data['meta']['expire_date'] ?? $time) < $time) {
                     $pastes[] = $pasteid;
                     if (++$count >= $batchsize) {
                         break;
diff --git a/lib/Data/GoogleCloudStorage.php b/lib/Data/GoogleCloudStorage.php
index 2ebfb7fe..670dc52e 100644
--- a/lib/Data/GoogleCloudStorage.php
+++ b/lib/Data/GoogleCloudStorage.php
@@ -107,7 +107,7 @@ class GoogleCloudStorage extends AbstractData
      */
     private function _upload($key, &$payload)
     {
-        $metadata = array_key_exists('meta', $payload) ? $payload['meta'] : array();
+        $metadata = $payload['meta'] ?? array();
         unset($metadata['salt']);
         foreach ($metadata as $k => $v) {
             $metadata[$k] = strval($v);
diff --git a/lib/Data/S3Storage.php b/lib/Data/S3Storage.php
index 575f90f4..b1c4a269 100644
--- a/lib/Data/S3Storage.php
+++ b/lib/Data/S3Storage.php
@@ -165,7 +165,7 @@ class S3Storage extends AbstractData
      */
     private function _upload($key, &$payload)
     {
-        $metadata = array_key_exists('meta', $payload) ? $payload['meta'] : array();
+        $metadata = $payload['meta'] ?? array();
         unset($metadata['salt']);
         foreach ($metadata as $k => $v) {
             $metadata[$k] = strval($v);
diff --git a/lib/Model/Paste.php b/lib/Model/Paste.php
index 2b5d9f81..9b55cb71 100644
--- a/lib/Model/Paste.php
+++ b/lib/Model/Paste.php
@@ -73,10 +73,7 @@ class Paste extends AbstractModel
         }
 
         // check if non-expired burn after reading paste needs to be deleted
-        if (
-            array_key_exists('adata', $data) &&
-            $data['adata'][self::ADATA_BURN_AFTER_READING] === 1
-        ) {
+        if (($data['adata'][self::ADATA_BURN_AFTER_READING] ?? 0) === 1) {
             $this->delete();
         }
 
@@ -207,8 +204,7 @@ class Paste extends AbstractModel
         if (!array_key_exists('adata', $this->_data) && !array_key_exists('data', $this->_data)) {
             $this->get();
         }
-        return array_key_exists('adata', $this->_data) &&
-            $this->_data['adata'][self::ADATA_OPEN_DISCUSSION] === 1;
+        return ($this->_data['adata'][self::ADATA_OPEN_DISCUSSION] ?? 0) === 1;
     }
 
     /**
@@ -222,12 +218,9 @@ class Paste extends AbstractModel
         $expiration = $data['meta']['expire'] ?? 0;
         unset($data['meta']['expire']);
         $expire_options = $this->_conf->getSection('expire_options');
-        if (array_key_exists($expiration, $expire_options)) {
-            $expire = $expire_options[$expiration];
-        } else {
-            // using getKey() to ensure a default value is present
-            $expire = $this->_conf->getKey($this->_conf->getKey('default', 'expire'), 'expire_options');
-        }
+        // using getKey() to ensure a default value is present
+        $expire = $expire_options[$expiration] ??
+            $this->_conf->getKey($this->_conf->getKey('default', 'expire'), 'expire_options');
         if ($expire > 0) {
             $data['meta']['expire_date'] = time() + $expire;
         }
diff --git a/lib/Proxy/ShlinkProxy.php b/lib/Proxy/ShlinkProxy.php
index 639a957c..93c3be27 100644
--- a/lib/Proxy/ShlinkProxy.php
+++ b/lib/Proxy/ShlinkProxy.php
@@ -71,11 +71,6 @@ class ShlinkProxy extends AbstractProxy
      */
     protected function _extractShortUrl(array $data): ?string
     {
-        if (
-            array_key_exists('shortUrl', $data)
-        ) {
-            return $data['shortUrl'];
-        }
-        return null;
+        return $data['shortUrl'] ?? null;
     }
 }
diff --git a/lib/Proxy/YourlsProxy.php b/lib/Proxy/YourlsProxy.php
index ae9e11e7..3eea7e15 100644
--- a/lib/Proxy/YourlsProxy.php
+++ b/lib/Proxy/YourlsProxy.php
@@ -65,12 +65,8 @@ class YourlsProxy extends AbstractProxy
      */
     protected function _extractShortUrl(array $data): ?string
     {
-        if (
-            array_key_exists('statusCode', $data) &&
-            $data['statusCode'] == 200 &&
-            array_key_exists('shorturl', $data)
-        ) {
-            return $data['shorturl'];
+        if (($data['statusCode'] ?? 0) == 200) {
+            return $data['shorturl'] ?? 0;
         }
         return null;
     }
diff --git a/lib/Request.php b/lib/Request.php
index fb6fb37c..71c6ea94 100644
--- a/lib/Request.php
+++ b/lib/Request.php
@@ -104,7 +104,7 @@ class Request
         $this->_isJsonApi = $this->_detectJsonRequest();
 
         // parse parameters, depending on request type
-        switch (array_key_exists('REQUEST_METHOD', $_SERVER) ? $_SERVER['REQUEST_METHOD'] : 'GET') {
+        switch ($_SERVER['REQUEST_METHOD'] ?? 'GET') {
             case 'DELETE':
             case 'PUT':
             case 'POST':
@@ -204,8 +204,7 @@ class Request
      */
     public function getParam($param, $default = '')
     {
-        return array_key_exists($param, $this->_params) ?
-            $this->_params[$param] : $default;
+        return $this->_params[$param] ?? $default;
     }
 
     /**
@@ -263,23 +262,22 @@ class Request
      */
     private function _detectJsonRequest()
     {
-        $hasAcceptHeader = array_key_exists('HTTP_ACCEPT', $_SERVER);
-        $acceptHeader    = $hasAcceptHeader ? $_SERVER['HTTP_ACCEPT'] : '';
+        $acceptHeader = $_SERVER['HTTP_ACCEPT'] ?? '';
 
         // simple cases
         if (
-            (array_key_exists('HTTP_X_REQUESTED_WITH', $_SERVER) &&
-                $_SERVER['HTTP_X_REQUESTED_WITH'] == 'JSONHttpRequest') ||
-            ($hasAcceptHeader &&
+            ($_SERVER['HTTP_X_REQUESTED_WITH'] ?? '' ) == 'JSONHttpRequest' ||
+            (
                 str_contains($acceptHeader, self::MIME_JSON) &&
                 !str_contains($acceptHeader, self::MIME_HTML) &&
-                !str_contains($acceptHeader, self::MIME_XHTML))
+                !str_contains($acceptHeader, self::MIME_XHTML)
+            )
         ) {
             return true;
         }
 
         // advanced case: media type negotiation
-        if ($hasAcceptHeader) {
+        if (!empty($acceptHeader)) {
             $mediaTypes = array();
             foreach (explode(',', trim($acceptHeader)) as $mediaTypeRange) {
                 if (preg_match(