diff --git a/README.md b/README.md
index 6075f8c6..b809cde8 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ Integrates with :
  - Users have the ability to login, change their password or vacation (out of office) status.
  - Integration with Squirrelmail / Roundcube (via plugins)
  - Optional XMLRPC based API 
- - Supports PHP5.4+
+ - Supports PHP5.6+
 
 ## Useful Links
 
diff --git a/common.php b/common.php
index 4766df5f..2c4e741a 100644
--- a/common.php
+++ b/common.php
@@ -8,7 +8,6 @@
  *
  * Further details on the project are available at http://postfixadmin.sf.net
  *
- * @version $Id$
  * @license GNU GPL v2 or later.
  *
  * File: common.php
diff --git a/composer.json b/composer.json
index 33cd3344..0a3b25be 100644
--- a/composer.json
+++ b/composer.json
@@ -34,8 +34,7 @@
     "autoload": {
         "files": [
             "config.inc.php",
-            "functions.inc.php",
-            "lib/smarty/libs/bootstrap.php"
+            "functions.inc.php"
         ]
     }
 }
diff --git a/config.inc.php b/config.inc.php
index 88b9cf79..c6020823 100644
--- a/config.inc.php
+++ b/config.inc.php
@@ -8,7 +8,6 @@
  * 
  * Further details on the project are available at http://postfixadmin.sf.net 
  * 
- * @version $Id$ 
  * @license GNU GPL v2 or later. 
  * 
  * File: config.inc.php
diff --git a/functions.inc.php b/functions.inc.php
index 5407f7cd..c7f202c9 100644
--- a/functions.inc.php
+++ b/functions.inc.php
@@ -8,7 +8,6 @@
  *
  * Further details on the project are available at http://postfixadmin.sf.net
  *
- * @version $Id$
  * @license GNU GPL v2 or later.
  *
  * File: functions.inc.php
@@ -665,11 +664,6 @@ function list_domains_for_admin($username) {
     return array_column($result, 'domain');
 }
 
-
-if (!function_exists('array_column')) {
-    require_once(dirname(__FILE__) . '/lib/array_column.php');
-}
-
 /**
  * List all available domains.
  *
@@ -1916,15 +1910,10 @@ function db_in_clause($field, array $values) {
  *                           Note: the $searchmode operator will only be used if a $condition for that field is set.
  *                                 This also means you'll need to set a (dummy) condition for NULL and NOTNULL.
  */
-function db_where_clause($condition, $struct, $additional_raw_where = '', $searchmode = array()) {
-    if (!is_array($condition)) {
-        throw new Exception('db_where_cond: parameter $cond is not an array!');
-    } elseif (!is_array($searchmode)) {
-        throw new Exception('db_where_cond: parameter $searchmode is not an array!');
-    } elseif (count($condition) == 0 && trim($additional_raw_where) == '') {
+function db_where_clause(array $condition, array $struct, $additional_raw_where = '', array $searchmode = array()) {
+
+    if (count($condition) == 0 && trim($additional_raw_where) == '') {
         throw new Exception("db_where_cond: parameter is an empty array!");
-    } elseif (!is_array($struct)) {
-        throw new Exception('db_where_cond: parameter $struct is not an array!');
     }
 
     $allowed_operators = array('<', '>', '>=', '<=', '=', '!=', '<>', 'CONT', 'LIKE', 'NULL', 'NOTNULL');
diff --git a/lib/array_column.php b/lib/array_column.php
deleted file mode 100644
index d712823b..00000000
--- a/lib/array_column.php
+++ /dev/null
@@ -1,8 +0,0 @@
-<?php
-function array_column(array $array, $column) {
-    $retval = array();
-    foreach ($array as $row) {
-        $retval[] = $row[$column];
-    }
-    return $retval;
-}
diff --git a/lib/block_random_int.php b/lib/block_random_int.php
index cf0f3b3b..765107e8 100644
--- a/lib/block_random_int.php
+++ b/lib/block_random_int.php
@@ -1,14 +1,17 @@
 <?php
+
 /**
  * This file should only be loaded if you're : 
  *  a. running PHP < 7.0, and
  *  b. have the php_crypt password hash configured, and
  *  c. have not loaded paragonie's random_compat library.
+ *
  */
 
 if(function_exists('random_int')) {
     return;
 }
+
 function random_int() { // someone might not be using php_crypt or ask for password generation, in which case random_int() won't be called
         die(__FILE__ . " Postfixadmin security: Please install https://github.com/paragonie/random_compat OR enable the 'Phar' extension.");
 }
diff --git a/model/DomainHandler.php b/model/DomainHandler.php
index 5102bdcc..dabe770e 100644
--- a/model/DomainHandler.php
+++ b/model/DomainHandler.php
@@ -263,7 +263,7 @@ class DomainHandler extends PFAHandler {
      * @return boolean
      */
     protected function domain_postcreation() {
-        $script=Config::read('domain_postcreation_script');
+        $script=Config::read_string('domain_postcreation_script');
 
         if (empty($script)) {
             return true;
@@ -295,7 +295,7 @@ class DomainHandler extends PFAHandler {
      * @return boolean
      */
     protected function domain_postdeletion() {
-        $script=Config::read('domain_postdeletion_script');
+        $script=Config::read_string('domain_postdeletion_script');
 
         if (empty($script)) {
             return true;
diff --git a/model/MailboxHandler.php b/model/MailboxHandler.php
index 4ef361b4..6c6c7e6d 100644
--- a/model/MailboxHandler.php
+++ b/model/MailboxHandler.php
@@ -561,10 +561,10 @@ class MailboxHandler extends PFAHandler {
      */
     protected function mailbox_post_script() {
         if ($this->new) {
-            $cmd = Config::read('mailbox_postcreation_script');
+            $cmd = Config::read_string('mailbox_postcreation_script');
             $warnmsg = Config::Lang('mailbox_postcreate_failed');
         } else {
-            $cmd = Config::read('mailbox_postedit_script');
+            $cmd = Config::read_string('mailbox_postedit_script');
             $warnmsg = Config::Lang('mailbox_postedit_failed');
         }
 
@@ -608,7 +608,7 @@ class MailboxHandler extends PFAHandler {
      * also adds a detailed error message to $this->errormsg[]
      */
     protected function mailbox_postdeletion() {
-        $cmd = Config::read('mailbox_postdeletion_script');
+        $cmd = Config::read_string('mailbox_postdeletion_script');
 
         if (empty($cmd)) {
             return true;
@@ -735,8 +735,8 @@ class MailboxHandler extends PFAHandler {
 
     /**
      * @return boolean true on success; false on failure
+     * @param string $new_password
      * @param string $old_password
-     * @param string $new_passwords
      * @param bool $match = true
      *
      * All passwords need to be plain text; they'll be hashed appropriately
diff --git a/model/PFAHandler.php b/model/PFAHandler.php
index 8243d451..97600c04 100644
--- a/model/PFAHandler.php
+++ b/model/PFAHandler.php
@@ -33,12 +33,12 @@ abstract class PFAHandler {
      * @var string (default) name of the database table
      * (can be overridden by $CONF[database_prefix] and $CONF[database_tables][*] via table_by_key())
      */
-    protected $db_table;
+    protected $db_table = '';
 
     /**
      * @var string field containing the ID
      */
-    protected $id_field;
+    protected $id_field = '';
 
     /**
      * @var string  field containing the label
@@ -52,7 +52,7 @@ abstract class PFAHandler {
      * defaults to $id_field if not set
      * @var string
      */
-    protected $order_by;
+    protected $order_by = '';
 
     /**
      * @var string
@@ -215,6 +215,9 @@ abstract class PFAHandler {
 
         $this->initStruct();
 
+        /**
+         * @psalm-suppress InvalidArrayOffset
+         */
         if (!isset($this->struct['_can_edit'])) {
             $this->struct['_can_edit'] = pacol(0,           0,      1,      'vnum', ''                   , ''                  , '', array(),
                 /*not_in_db*/ 0,
@@ -223,6 +226,9 @@ abstract class PFAHandler {
                 );
         }
 
+        /**
+         * @psalm-suppress InvalidArrayOffset
+         */
         if (!isset($this->struct['_can_delete'])) {
             $this->struct['_can_delete'] = pacol(0,         0,      1,      'vnum', ''                   , ''                  , '', array(),
                 /*not_in_db*/ 0,
@@ -231,7 +237,10 @@ abstract class PFAHandler {
                 );
         }
 
-        $struct_hook = Config::read($this->db_table . '_struct_hook');
+        if(empty($this->db_table)) {
+            throw new Exception("db_table not defined");
+        }
+        $struct_hook = Config::read_string($this->db_table . '_struct_hook');
         if (!empty($struct_hook) && is_string($struct_hook) && $struct_hook != 'NO' && function_exists($struct_hook)) {
             $this->struct = $struct_hook($this->struct);
         }
@@ -810,15 +819,7 @@ abstract class PFAHandler {
             $real_condition = $condition;
         }
 
-        $result = $this->read_from_db($real_condition, $searchmode, $limit, $offset);
-
-        if (!is_array($result)) {
-            error_log('getList: read_from_db didn\'t return an array. table: ' . $this->db_table . ' - condition: $condition - limit: $limit - offset: $offset');
-            error_log('getList: This is most probably caused by read_from_db_postprocess()');
-            die('Unexpected error while reading from database! (Please check the error log for details, and open a bugreport)');
-        }
-
-        $this->result = $result;
+        $this->result = $this->read_from_db($real_condition, $searchmode, $limit, $offset);
         return true;
     }
 
diff --git a/psalm.xml b/psalm.xml
index df696107..08df1553 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -12,6 +12,7 @@
             <directory name="tests" />
             <directory name="templates_c" />
             <directory name="lib/smarty" />
+            <file name="lib/block_random_int.php" />
             <directory name="ADDITIONS/" />
         </ignoreFiles>
     </projectFiles>
diff --git a/public/upgrade.php b/public/upgrade.php
index 2ae20eef..ac98a077 100644
--- a/public/upgrade.php
+++ b/public/upgrade.php
@@ -7,7 +7,7 @@ if (!defined('POSTFIXADMIN')) {
     require_once('common.php');
 }
 
-if (!isset($CONF) || !is_array($CONF)) {
+if (empty($CONF)) {
     die("config.inc.php seems invalid");
 }