Do not connect to mysql in __construct

MysqliDb.php

@@ -167,11 +167,6 @@ class MysqliDb
             $this->isSubQuery = true;
             return;
         }
-
-        // for subqueries we do not need database connection and redefine root instance
-        if (!is_object ($host))
-            $this->connect();
-
         $this->setPrefix();
         self::$_instance = $this;
     }
@@ -192,8 +187,19 @@ class MysqliDb
             or die('There was a problem connecting to the database');
 
         if ($this->charset)
-            $this->_mysqli->set_charset ($this->charset);
+            $this->mysqli()->set_charset ($this->charset);
+    }
+
+    /**
+     * A method to get mysqli object or create it in case needed
+     */
+    public function mysqli ()
+    {
+        if (!$this->_mysqli)
+            $this->connect();
+        return $this->_mysqli;
     }
+
     /**
      * A method of returning the static instance to allow access to the
      * instantiated object from within another class.
@@ -643,7 +649,7 @@ class MysqliDb
      */
     public function getInsertId()
     {
-        return $this->_mysqli->insert_id;
+        return $this->mysqli()->insert_id;
     }
 
     /**
@@ -655,7 +661,7 @@ class MysqliDb
      */
     public function escape($str)
     {
-        return $this->_mysqli->real_escape_string($str);
+        return $this->mysqli()->real_escape_string($str);
     }
 
     /**
@@ -667,7 +673,7 @@ class MysqliDb
      * @return bool True if connection is up
      */
     public function ping() {
-        return $this->_mysqli->ping();
+        return $this->mysqli()->ping();
     }
 
     /**
@@ -876,11 +882,11 @@ class MysqliDb
             array_push($results, $x);
         }
         // stored procedures sometimes can return more then 1 resultset
-        if ($this->_mysqli->more_results())
-            $this->_mysqli->next_result();
+        if ($this->mysqli()->more_results())
+            $this->mysqli()->next_result();
 
         if (in_array ('SQL_CALC_FOUND_ROWS', $this->_queryOptions)) {
-            $stmt = $this->_mysqli->query ('SELECT FOUND_ROWS()');
+            $stmt = $this->mysqli()->query ('SELECT FOUND_ROWS()');
             $totalCount = $stmt->fetch_row();
             $this->totalCount = $totalCount[0];
         }
@@ -1074,8 +1080,8 @@ class MysqliDb
      */
     protected function _prepareQuery()
     {
-        if (!$stmt = $this->_mysqli->prepare($this->_query)) {
-            trigger_error("Problem preparing query ($this->_query) " . $this->_mysqli->error, E_USER_ERROR);
+        if (!$stmt = $this->mysqli()->prepare($this->_query)) {
+            trigger_error("Problem preparing query ($this->_query) " . $this->mysqli()->error, E_USER_ERROR);
         }
         if ($this->traceEnabled)
             $this->traceStartQ = microtime (true);
@@ -1091,7 +1097,7 @@ class MysqliDb
         if (!$this->isSubQuery)
             return;
         if ($this->_mysqli)
-            $this->_mysqli->close();
+            $this->mysqli()->close();
     }
 
     /**
@@ -1151,7 +1157,9 @@ class MysqliDb
      * @return string
      */
     public function getLastError () {
-        return trim ($this->_stmtError . " " . $this->_mysqli->error);
+        if (!$this->_mysqli)
+            return "mysqli is null";
+        return trim ($this->_stmtError . " " . $this->mysqli()->error);
     }
 
     /**
@@ -1276,7 +1284,7 @@ class MysqliDb
      * @uses register_shutdown_function(array($this, "_transaction_shutdown_check"))
      */
     public function startTransaction () {
-        $this->_mysqli->autocommit (false);
+        $this->mysqli()->autocommit (false);
         $this->_transaction_in_progress = true;
         register_shutdown_function (array ($this, "_transaction_status_check"));
     }
@@ -1288,9 +1296,9 @@ class MysqliDb
      * @uses mysqli->autocommit(true);
      */
     public function commit () {
-        $this->_mysqli->commit ();
+        $this->mysqli()->commit ();
         $this->_transaction_in_progress = false;
-        $this->_mysqli->autocommit (true);
+        $this->mysqli()->autocommit (true);
     }
 
     /**
@@ -1300,9 +1308,9 @@ class MysqliDb
      * @uses mysqli->autocommit(true);
      */
     public function rollback () {
-      $this->_mysqli->rollback ();
+      $this->mysqli()->rollback ();
       $this->_transaction_in_progress = false;
-      $this->_mysqli->autocommit (true);
+      $this->mysqli()->autocommit (true);
     }
 
     /**

tests/mysqliDbTests.php

@@ -112,6 +112,12 @@ foreach ($tables as $name => $fields) {
     createTable ($prefix.$name, $fields);
 }
 
+if (!$db->ping()) {
+    echo "db is not up";
+    exit;
+}
+
+$str = $db->escape ("te'st");
 // insert test with autoincrement
 foreach ($data as $name => $datas) {
     foreach ($datas as $d) {