diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index df6f0e51e..9f4dd7ea2 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -1,4 +1,4 @@
-name: PHP Composer
+name: PHP Composer & PHPStan
 
 on:
   push:
@@ -69,3 +69,7 @@ jobs:
     - name: Run test suite for library
       run: |
         php ./src/vendor/bin/phpunit ./tests/library/
+
+    - name: Run PHPStan analysis
+      uses: php-actions/phpstan@v3
+      configuration: phpstan.neon
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
new file mode 100644
index 000000000..e62ff6343
--- /dev/null
+++ b/phpstan-baseline.neon
@@ -0,0 +1,71 @@
+parameters:
+	ignoreErrors:
+		-
+			message: "#^Caught class Stripe\\\\Error\\\\ApiConnection not found\\.$#"
+			count: 1
+			path: src/library/Payment/Adapter/Stripe.php
+
+		-
+			message: "#^Caught class Stripe\\\\Error\\\\Authentication not found\\.$#"
+			count: 1
+			path: src/library/Payment/Adapter/Stripe.php
+
+		-
+			message: "#^Caught class Stripe\\\\Error\\\\Card not found\\.$#"
+			count: 1
+			path: src/library/Payment/Adapter/Stripe.php
+
+		-
+			message: "#^Caught class Stripe\\\\Error\\\\InvalidRequest not found\\.$#"
+			count: 1
+			path: src/library/Payment/Adapter/Stripe.php
+
+		-
+			message: "#^Call to an undefined method Payment_AdapterAbstract\\:\\:init\\(\\)\\.$#"
+			count: 1
+			path: src/library/Payment/AdapterAbstract.php
+
+		-
+			message: "#^Method Registrar_Adapter_Internetbs\\:\\:_process\\(\\) should return array but return statement is missing\\.$#"
+			count: 1
+			path: src/library/Registrar/Adapter/Internetbs.php
+
+		-
+			message: "#^Method Registrar_Adapter_Internetbs\\:\\:getDomainDetails\\(\\) should return Registrar_Domain but return statement is missing\\.$#"
+			count: 1
+			path: src/library/Registrar/Adapter/Internetbs.php
+
+		-
+			message: "#^Undefined variable\\: \\$client_id$#"
+			count: 1
+			path: src/library/Server/Manager/Ispconfig3.php
+
+		-
+			message: "#^Undefined variable\\: \\$section$#"
+			count: 1
+			path: src/library/Server/Manager/Ispconfig3.php
+
+		-
+			message: "#^Access to an undefined property Server_Manager_Plesk\\:\\:\\$_client\\.$#"
+			count: 23
+			path: src/library/Server/Manager/Plesk.php
+
+		-
+			message: "#^Method Server_Manager_Plesk\\:\\:changeAccountDomain\\(\\) should return bool but return statement is missing\\.$#"
+			count: 1
+			path: src/library/Server/Manager/Plesk.php
+
+		-
+			message: "#^Method Server_Manager_Plesk\\:\\:testConnection\\(\\) should return bool but return statement is missing\\.$#"
+			count: 1
+			path: src/library/Server/Manager/Plesk.php
+
+		-
+			message: "#^Undefined variable\\: \\$client$#"
+			count: 10
+			path: src/library/Server/Manager/Plesk.php
+
+		-
+			message: "#^Undefined variable\\: \\$domainId$#"
+			count: 1
+			path: src/library/Server/Manager/Plesk.php
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 000000000..1170d0f12
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,26 @@
+includes:
+	- phpstan-baseline.neon
+
+parameters:
+	level: 0
+	paths:
+		- src
+	excludePaths:
+		analyse:
+		- src/vendor
+		- src/rb.php
+		- src/library/Registrar/Adapter/srsx.php
+		- src/library/Box/Request.php
+		- src/library/Server/Manager/Custom.php
+	ignoreErrors:
+		- '#^Function __trans not found\.$#'
+		- message: '#^Function rmAllDir not found\.$#'
+		  path: src/install/install.php
+		- message: '#^Access to an undefined property FOSSPatchAbstract\:\:\$di\.$#'
+		  path: src/foss-update.php
+		- '#^Inner named functions are not supported by PHPStan\. Consider refactoring to an anonymous function, class method, or a top\-level\-defined function\. See issue \#165 \(https\://github\.com/phpstan/phpstan/issues/165\) for more details\.$#'
+		- message: '#^Result of function curl_close \(void\) is used\.$#'
+		  path: src/modules/Spamchecker/akismet.curl.class.php
+		- message: '#^Result of function header \(void\) is used\.$#'
+		  path: src/modules/Custompages/Controller/Client.php
+		- '#^Method Box\\Mod\\Currency\\Service\:\:_getRate\(\) should return float but return statement is missing\.$#'
diff --git a/src/di.php b/src/di.php
index 7573efc89..230b00c3b 100644
--- a/src/di.php
+++ b/src/di.php
@@ -389,12 +389,6 @@ $di['license_server'] = function () use ($di) {
     return $server;
 };
 
-$di['service_boxbilling'] = $di->protect(function ($config) {
-    $service = new \Box\Mod\Serviceboxbillinglicense\ServiceBoxbilling($config);
-
-    return $service;
-});
-
 $di['ftp'] = $di->protect(function ($params) { return new \Box_Ftp($params); });
 
 $di['geoip'] = function () { return new \GeoIp2\Database\Reader(PATH_LIBRARY . '/GeoLite2-Country.mmdb'); };
diff --git a/src/library/Box/DbLoggedPDOStatement.php b/src/library/Box/DbLoggedPDOStatement.php
index 65b3b23ea..12d61f350 100644
--- a/src/library/Box/DbLoggedPDOStatement.php
+++ b/src/library/Box/DbLoggedPDOStatement.php
@@ -15,9 +15,9 @@
 
 class Box_DbLoggedPDOStatement extends PDOStatement
 {
-    public function execute ($input_parameters = null)
+    public function execute ($input_parameters = null): bool
     {
         error_log($this->queryString);
-        parent::execute($input_parameters);
+        return parent::execute($input_parameters);
     }
 }
\ No newline at end of file
diff --git a/src/library/Box/Extension.php b/src/library/Box/Extension.php
index 7b3911d93..e3151ab35 100644
--- a/src/library/Box/Extension.php
+++ b/src/library/Box/Extension.php
@@ -63,7 +63,7 @@
             $params = array();
             $params['type'] = $type;
             $params['id'] = $id;
-            return $this->_request('extension/' . $params['id'] . '/version');
+            return $this->_request('extension/' . $params['id'] . '/version', $params);
         }
 
         public function getLatest($type = null)
diff --git a/src/library/Server/Manager/Vesta.php b/src/library/Server/Manager/Vesta.php
index 2cc18fdcd..6e8a5dc6c 100644
--- a/src/library/Server/Manager/Vesta.php
+++ b/src/library/Server/Manager/Vesta.php
@@ -343,7 +343,7 @@ class Server_Manager_Vesta extends Server_Manager
             'returncode' => $vst_returncode,
             'cmd' => $vst_command,
             'arg1' => $a->getUsername(),
-            'arg2' => $this->create_tmp_file($new),
+            'arg2' => $new,
         ];
         // Make request and change password
         $result = $this->_makeRequest($postvars);
diff --git a/src/library/Server/Manager/Whm.php b/src/library/Server/Manager/Whm.php
index ef106830f..b6678614d 100644
--- a/src/library/Server/Manager/Whm.php
+++ b/src/library/Server/Manager/Whm.php
@@ -632,12 +632,7 @@ class xmlapi {
 		if ( (defined('XMLAPI_DEBUG')) && (XMLAPI_DEBUG == '1') ) {
 		 	$this->debug = true;
 		}
-
-		// Check if raw xml output must be enabled
-		if ( (defined('XMLAPI_RAW_XML')) && (XMLAPI_RAW_XML == '1') ) {
-		 	$this->raw_xml = true;
-		}
-		
+	
 		/**
 		* Authentication
 		* This can either be passed at this point or by using the set_hash or set_password functions
@@ -1907,7 +1902,7 @@ class xmlapi {
 	* @link http://docs.cpanel.net/twiki/bin/view/AllDocumentation/AutomationIntegration/EditPackage XML API Call documentation
 	*/
 	public function editpkg($pkg) {
-		if (!$isset($pkg['name'])) {
+		if (!isset($pkg['name'])) {
 			error_log("editpkg requires that name is defined in the array passed to it");
 			return false;
 		}
diff --git a/src/modules/Cron/Service.php b/src/modules/Cron/Service.php
index 7e5199ba0..cb40e173d 100644
--- a/src/modules/Cron/Service.php
+++ b/src/modules/Cron/Service.php
@@ -103,8 +103,8 @@ class Service
     {
         try {
             $api->{$method}($params);
-        } catch (Exception $e) {
-            throw new Exception($e);
+        } catch (\Exception $e) {
+            throw new \Exception($e);
         } finally {
             if ('cli' == php_sapi_name()) {
                 echo "\e[32mSuccessfully ran " . $method . '(' . $params . ')' . ".\e[0m\n";
diff --git a/src/modules/Currency/Service.php b/src/modules/Currency/Service.php
index ce0eca61f..99acbc6b5 100644
--- a/src/modules/Currency/Service.php
+++ b/src/modules/Currency/Service.php
@@ -364,7 +364,6 @@ class Service implements InjectionAwareInterface
      *
      * @since 4.22.0
      *
-     * @return string
      */
     public function updateKey($key)
     {
@@ -372,7 +371,7 @@ class Service implements InjectionAwareInterface
         $values = [':key' => $key];
 
         $db = $this->di['db'];
-        $currency = $db->exec($sql, $values);
+        $db->exec($sql, $values);
     }
 
     /**
@@ -380,7 +379,7 @@ class Service implements InjectionAwareInterface
      *
      * @since 4.22.0
      *
-     * @return string
+     * @return bool
      */
     public function isCronEnabled()
     {
@@ -403,7 +402,6 @@ class Service implements InjectionAwareInterface
      *
      * @var int
      *
-     * @return string
      */
     public function setCron($data)
     {
@@ -418,7 +416,7 @@ class Service implements InjectionAwareInterface
         $values = [':key' => $key];
 
         $db = $this->di['db'];
-        $currency = $db->exec($sql, $values);
+        $db->exec($sql, $values);
     }
 
     public function toApiArray(\Model_Currency $model)
diff --git a/src/modules/Extension/Service.php b/src/modules/Extension/Service.php
index a634599f1..3b77d2e67 100644
--- a/src/modules/Extension/Service.php
+++ b/src/modules/Extension/Service.php
@@ -515,8 +515,8 @@ class Service implements InjectionAwareInterface
         }
 
         $info = $mod->getManifest();
-        if (isset($info['minimum_boxbilling_version']) && Box_Version::compareVersion($info['minimum_boxbilling_version']) > 0) {
-            throw new \Box_Exception('Module can not be installed. It requires at least :min version of FOSSBilling. You are using :v', [':min' => $info['minimum_boxbilling_version'], ':v' => Box_Version::VERSION]);
+        if (isset($info['minimum_boxbilling_version']) && \Box_Version::compareVersion($info['minimum_boxbilling_version']) > 0) {
+            throw new \Box_Exception('Module can not be installed. It requires at least :min version of FOSSBilling. You are using :v', [':min' => $info['minimum_boxbilling_version'], ':v' => \Box_Version::VERSION]);
         }
 
         // Allow install module even if no installer exists
diff --git a/src/modules/Massmailer/Service.php b/src/modules/Massmailer/Service.php
index 1e50369a6..70738413e 100644
--- a/src/modules/Massmailer/Service.php
+++ b/src/modules/Massmailer/Service.php
@@ -160,7 +160,7 @@ class Service implements \Box\InjectionAwareInterface
             'client_id' => $client_id,
         ];
 
-        $extensionService = $di['mod_service']('extension');
+        $extensionService = $this->di['mod_service']('extension');
         if ($extensionService->isExtensionActive('mod', 'demo')) {
             throw new \Box_Exception('Disabled for security reasons (Demo mode enabled)');
         }
diff --git a/src/modules/Theme/Controller/Admin.php b/src/modules/Theme/Controller/Admin.php
index 2c8ce2ce9..acc73bb7f 100644
--- a/src/modules/Theme/Controller/Admin.php
+++ b/src/modules/Theme/Controller/Admin.php
@@ -47,7 +47,6 @@ class Admin implements \Box\InjectionAwareInterface
      *
      * @param string $code - client area theme code
      *
-     * @return array
      */
     public function save_theme_settings(\Box_App $app, $theme)
     {