cast function call parameters to strings or arrays

The SAPNWRFC module by Piers Harding on PHP 5.5 would throw an exception
in case parameters were anything other than strings. All other modules
(saprfc by Koucky on PHP 5.5 and sapnwrfc by Kralik on PHP 7.x) don't
behave that way.

src/Traits/ParamTrait.php

@@ -28,7 +28,7 @@ private function getInputParams($inputs, $params)
         foreach ($inputs as $input) {
             $key = $input->getName();
             if (array_key_exists($key, $params)) {
-                $result[$key] = $params[$key];
+                $result[$key] = $this->typeCastParam($params[$key]);
             } elseif (!$input->isOptional()) {
                 throw new FunctionCallException(sprintf(
                     'Missing parameter \'%s\' for function call \'%s\'!',
@@ -40,6 +40,25 @@ private function getInputParams($inputs, $params)
         return $result;
     }
 
+    /**
+     * Typecast a remote function call parameter.
+     *
+     * The SAPNWRFC module by Piers Harding on PHP 5.5 would throw an exception
+     * in case parameters were anything other than strings. All other modules
+     * (saprfc by Koucky on PHP 5.5 and sapnwrfc by Kralik on PHP 7.x) don't
+     * behave that way.
+     *
+     * @param mixed $param The parameter to typecast.
+     * @return string|array
+     */
+    private function typeCastParam($param)
+    {
+        if (is_array($param) || is_string($param)) {
+            return $param;
+        }
+        return (string)$param;
+    }
+
     /**
      * Generate a function call parameter array from a list of known tables and the
      * previously set parameters.