fine tune of code, detailed tests added

src/Client.php

@@ -409,7 +409,7 @@ class Client implements Interfaces\ClientInterface
             $this->openSocket();
 
             // If socket is active
-            if ($this->getSocket()) {
+            if (null !== $this->getSocket()) {
 
                 // If we logged in then exit from loop
                 if (true === $this->login()) {

src/Helpers/ArrayHelper.php

@@ -33,7 +33,7 @@ class ArrayHelper
     {
         $output = [];
         foreach ($keys as $key) {
-            if (!array_key_exists($key, $array) && empty($array[$key])) {
+            if (self::checkIfKeyNotExist($key, $array)) {
                 $output[] = $key;
             }
         }

src/SocketTrait.php

@@ -38,7 +38,7 @@ trait SocketTrait
         );
 
         // Throw error is socket is not initiated
-        if (!$socket) {
+        if (false === $socket) {
             throw new ClientException('Unable to establish socket session, ' . $this->_socket_err_str);
         }