mysqli constructor returns null

Question

I am trying to write a db util class using the singleton pattern. My problem is that the "connection" object is always null. The connection settings are correct. What could i be doing wrong ? Also, i am relatively new to php development. What method should i use to figure out what's wrong ? Code follows.

 class DBUtil { public $connection = NULL; //mysqli_connection object private static $instance = NULL; private function _constructor($conn){ //$this->connection = mysqli_connect(TagMetroConfiguration::getConfigurationValueFor("db_servser_name"), TagMetroConfiguration::getConfigurationValueFor("db_username"), TagMetroConfiguration::getConfigurationValueFor("db_password"), TagMetroConfiguration::getConfigurationValueFor("db_name")); $this->connection = new mysqli("localhost", "root", "toor", "testdb"); } public static function getInstance(){ if(DBUtil::$instance == NULL){ try{ DBUtil::$instance = new DBUtil(); }catch(Exception $ex){ throw new Exception("Unable to create DB Instance"); } } return DBUtil::$instance; } }

Well actually, the singleton pattern looks too complicated to you, but that's not a problem at all: Just don't use singletons. You don't need them in PHP. In your case you only need a global variable for the database connection. - But if you feel like copy and paste, the PHP manual has a code example for the Singleton Pattern (not that this makes anything better, don't use it ). Who needs singletons?. — hakre
– hakre, Commented Apr 11, 2012 at 14:27

Travesty3 · Accepted Answer · 2012-04-11 14:30:42Z

Your constructor function should be named __construct (notice two underscores).

Also, in your constructor, you have one parameter, $conn. When you call new DBUtil(), you are not providing that input parameter, so perhaps it's calling the default contructor, not your custom one.

If you want the input parameter $conn to be optional, try __construct($conn = null).

Or try calling it as new DBUtil(null).

Lee Davis · Accepted Answer · 2012-04-11 14:25:46Z

2

private function _constructor($conn) ??

should this be

private function __construct($conn)

answered Apr 11, 2012 at 14:25

Lee Davis

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Lee Davis Over a year ago

Also might want to set the default value to null, as your not passing a $conn variable when instantiating the object. private function __construct($conn = null)

Sudantha · Accepted Answer · 2012-04-17 22:19:06Z

2

There should be two underscores __ (__construct).

edited Apr 17, 2012 at 22:19

user142162

answered Apr 11, 2012 at 14:38

Sudantha

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Comments

jbrtrnd · Accepted Answer · 2012-04-11 14:28:22Z

You should do like this :

class DBUtil { private static $instance; private function _construct(){ $this->$instance = new mysqli("localhost", "root", "toor", "testdb"); } public static function getInstance(){ if(!isset(self::$instance){ try{ self::$instance = new DBUtil(); }catch(Exception $ex){ throw new Exception("Unable to create DB Instance"); } } return self::$instance; }

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