#10 Make query to constructor optional

Adds errors
Add NULL support for bind_param
Moves assignment of params so it can handle execute without a bind param

src/Statement.php

@@ -11,22 +11,42 @@ class Statement
     private $params;
     private $result;
     private $stored;
+    private $error;
 
-    public function __construct(Environment $environment, $query)
+    public function __construct(Environment $environment, $query = null)
     {
         $this->environment = $environment;
         $this->prepare($query);
     }
 
+    public function error()
+    {
+        return $this->error;
+    }
+
+    private function set_error($error)
+    {
+        $this->error = $error;
+        return false;
+    }
+
     public function bind_param($types, ...$params)
     {
-        $this->params = [];
+        $length = strlen($types);
+        if($this->query === null) {
+            return $this->set_error("Unable to perform a bind_param without a prepare");
+        } if($length != count($params)) {
+            return $this->set_error("bind_param's number of types in the string doesn't match number of parameters passed in");
+        }
+
         $param = current($params);
 
-        $length = strlen($types);
         for($i = 0; $i < $length; ++$i, $param = next($params)) {
             $type = $types[$i];
-            switch($type) {
+            if($type == null) {
+                $this->params[] = 'NULL';
+            } else {
+                switch($type) {
                 case 'i':
                     $this->params[] = (int) $param;
                     break;
@@ -37,13 +57,19 @@ public function bind_param($types, ...$params)
                 case 'o':
                     $this->params[] = "'". addslashes((string) $param) . "'";
                     break;
+                }
             }
         }
+
         return true;
     }
 
     public function execute()
     {
+        if($this->query === null) {
+            return $this->set_error("Unable to perform an execute without a prepare");
+        }
+
         $that = $this;
         $count = 0;
         $newQuery = preg_replace_callback(
@@ -53,35 +79,53 @@ function($match) use ($that, &$count) { return $that->params[$count++]; },
             );
         $result = $this->environment->query($newQuery);
         if($result instanceof ResultSet) {
-          $this->result = $result;
-          return true;
+            $this->result = $result;
+            return true;
         } else {
-          return $result;
+            return $result;
         }
     }
 
     public function prepare($query)
     {
         $this->query = $query;
+        $this->params = [];
         $this->result = null;
         $this->stored = false;
         return true;
       }
 
     public function store_result()
     {
+        if($this->query === null) {
+            return $this->set_error("Unable to perform a store_result without a prepare");
+        }
+
         $this->stored = true;
+        return true;
+    }
+
+    public function get_result()
+    {
+        if($this->query === null) {
+            return $this->set_error("Unable to perform a get_result without a prepare");
+        }
+
+        return $this->result;
     }
 
     public function result_metadata()
     {
-      return $this->result;
+        if($this->query === null) {
+            return $this->set_error("Unable to perform a result_metadata without a prepare");
+        }
+
+        return $this->result;
     }
 
     public function free_result()
     {
 
     }
 
-
 }