PHP: use a database within a class

Question

I already have a database file that connects to a database when I include it

class-database.php

class dbFactory {
    private static $host    = 'some.host.com';
    private static $name    = 'someDB';
    private static $user    = 'someUser';
    private static $pass    = 'somePassword';


    public function __construct() { }


    public static function pdo() {
        try {
            # MySQL with PDO_MYSQL
            return new PDO("mysql:host=$host;dbname=$name", $user, $pass);
            }
        catch(PDOException $e) {
            echo $e->getMessage();
            return null;
            exit;
            }  
    } // End: pdo()
} //End class

I usually access this by:

require( 'some-file-path' . 'class-database.php' );
$db = dbFactory::pdo();

Here is the question: How can I access $db from within another class?

For instance, if I have a class file called class-html.php and within that class (AKA, as part of the class code) I need something like...:

class-html.php

class html {
  ...some code...
  $db->query('SELECT * FROM tbl_head');
  ...some more code...
} //End: html

What I've been doing without success is:

require( 'some-file-path' . 'class-database.php' );
$db = dbFactory::pdo();

require( 'some-file-path' . 'class-html.php' );

I am getting error messages and am not sure what to do from here

In this case, both answers are what I need to resolve my problem. However, this site does not allows to accept two entries as the answers. What should I to? — Omar Juvera
– Omar Juvera, Commented Dec 19, 2013 at 23:19

kero · Accepted Answer · 2013-12-19 21:58:42Z

2

You can use a Singleton class

class dbFactory {

    //...
    private static $pdo_instance = null;

    private static function getPDOinstance() {
        if (self::$pdo_instance === null) {
            try {
                self::$pdo_instance = new PDO("...");
            } catch (PDOException $e) {
                //...
            }
        }
        return self::$pdo_instance;
    }

}

When you now access dbFactory::getPDOinstance() you'll only have one PDO instance of creating new ones inside each class using the DB

answered Dec 19, 2013 at 21:58

kero

10.7k5 gold badges44 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Stoic · Accepted Answer · 2013-12-19 22:04:57Z

1

Your class inside class-html.php can be modified a bit, along the following lines:

require( 'some-file-path' . 'class-database.php' );

class SomeClass {
  public $db;

  def __construct() {
    $db = dbFactory::getPDOinstance();
    // existing code ..
  }

  // other code      
}

Then, you can require the class as usual and:

require( 'some-file-path' . 'class-html.php' );
$obj = new SomeClass();
$obj->db->query('SELECT * FROM tbl_head')

UPDATE: This will create a new PDO instance if you instantiate SomeClass more than once.
UPDATE: Made use of kingkero's answer to use existing dbFactory instance, instead.

edited Dec 19, 2013 at 22:04

answered Dec 19, 2013 at 21:56

Stoic

10.8k6 gold badges44 silver badges62 bronze badges

6 Comments

eggyal Over a year ago

One may not want to create a new PDO object for every SomeClass object, nor for such objects to differ from those used elsewhere.

Omar Juvera Over a year ago

@stoic If an instance of a database initiated already, in this case $db, this "instance" cannot be accessed within another class (html) and that other class (html) has to create a whole new database instance? Am I correct?

kero Over a year ago

No, you can "save" the instance inside your dbFactory. You can read more about that in the wiki link I posted

Stoic Over a year ago

@Omar: Yeah, if you have an active instance of $db, then it will be different than the one that the above solution creates for you, i.e. the database instance is created, again. If you prefer (and you should) to use a single instance of $db make dbFactory a singleton class, as kingkero has done in his answer, and then use my method to call the appropriate behaviour. I will update my answer to build upon kingkero's answer.

Omar Juvera Over a year ago

@stoic Does it matters that SomeCalss's $db is public? Can it be private or protected or it really does not matters?

|

Collectives™ on Stack Overflow

PHP: use a database within a class

2 Answers 2

Comments

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related