PDO, PHP: Trying to instantiate object to call function - blank page

Question

So I have two files involved in this problem. One of them is the Database class and the other one is the file that include_once the Database file and then goes on to instantiate an object of that class to call a function -- getDB();. Thats's where it goes wrong.

Database class:

<?php
  class Database {           
    private static $datasource='mysql:host=localhost; dbname=db_name';
    private static $username='root';
    private static $password='root';
    private static $db;      

    private function __construct(){}

    public static function getDB(){ 
      if(!isset(self::$db)){ 
        try{
          self::$db=new PDO(self::$datasource,self::$username,self::$password); 
        }
        catch(PDOExceptin $e) {
          $error=$e->getMessage(); //variable $error can be used in the database_error.php file 
          //display database error file.  
          //include('database_error.php');
          exit();            
        }
      }
      return self::$db;      
    }

    function Database(){
      return new Database;
    }

  }

  ?>

And in my main file, I'm doing this:

 <?php
    include('partials/header.php'); 
    include_once('functions/pdo.php');

    $database = new Database();
    $getdb = $database->getDB();

    //Anything below won't show because of the failed instantiation of Database object above.
    //code..
 ?>

Obviously, I'm doing something wrong here. I'm running MAMP with php 5.3. How can I use my Database correctly? The reason I have a function with the same name as the class is because I read that you could instantiate the object with the function instead, but I didn't get that to work either...

var_dump($e); before exiting...

Denis de Bernardy
– Denis de Bernardy

2013-04-27 18:32:36 +00:00
Commented Apr 27, 2013 at 18:32 — Denis de Bernardy
– Denis de Bernardy, Commented Apr 27, 2013 at 18:32

bwoebi · Accepted Answer · 2013-04-27 18:41:59Z

2

You have a few errors here (use ini_set("display_errors", 1); error_reporting(-1); to see all your error messages):

The exception class of PDO is named PDOException and not PDOExceptin.

You call a static function from an non-static context: $database->getDb() where getDb is a static method. (write Database::getDb())

You write new Database which will result in a fatal error as the constructor is private (and named constructors have lower precedence than the magic method). Use there:

$getdb = Database::Database(); // and declare your Database method as static

edited Apr 27, 2013 at 18:41

answered Apr 27, 2013 at 18:36

bwoebi

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Denis de Bernardy · Accepted Answer · 2013-04-27 18:33:40Z

1

PDOExceptin should be PDOException.

Also, it helps to turn display_errors on and to install xdebug when developing.

answered Apr 27, 2013 at 18:33

Denis de Bernardy

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Comments

Your Common Sense · Accepted Answer · 2013-04-27 18:40:18Z

1

Obviously, I'm doing something wrong here.

Yes. you're writing way too much code.
The more code you write, the more errors you have. So, just get rid of all the useless code:

class Database {           
    private static $datasource='mysql:host=localhost; dbname=db_name';
    private static $username='root';
    private static $password='root';
    private static $db;      

    public static function getDB(){ 
      if(!isset(self::$db)){ 
          self::$db=new PDO(self::$datasource,self::$username,self::$password); 
      }
      return self::$db;      
    }
}

and call it this way

$db = Database::getDB();

answered Apr 27, 2013 at 18:40

Your Common Sense

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4 Comments

Denis de Bernardy Over a year ago

And then, one day he'll need two DB instances and... huhoh. :D

bwoebi Over a year ago

@Denis two DB instances? why? doesn't make any sense to have multiple instances... (If you don't need to manipulate data of different servers, which is a very very rare case)

Denis de Bernardy Over a year ago

@bwoebi: It depends on the app you use, on what you're doing, on whether you decided to scale by sharding your db, etc.

bwoebi Over a year ago

@Denis yes, but then you'll have some real abstraction layer who checks what to do ad you contain you connections in some static array etc....

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