Looking for a little help creating a DB class.

[kellendil]

I'm trying to make a very simple DB class, but haven't quite gotten the hang for using classes, to put it mildly.

Anyway, I'm making this class, with just a few functions, mainly to make, and use a class. Expanding on it later when I have a working one, should not be a big problem.

The class is, as mentioned, a database class, I want it to have the following 3 functions:
-Open a connection, with variables listed within the class
-Execute a query
-Close connection.

My own feeble attempt:
[code]
class database {

var $dbhost = 'serveradress';
var $dbusername = 'username';
var $dbpasswd = 'password'; 
var $database_name = 'dbname';

//open connection.
function sqlOpen($dbhost,$dbusername,$dbpasswd) {
$connection = mysql_connect("$dbhost","$dbusername","$dbpasswd")
or die ("Couldn't connect to server.");

$db = mysql_select_db("$database_name", $connection)
or die("Couldn't select database.");

return $db;
}

//close connection.
function sqlClose($connection) {
mysql_close($connection);
}
}[/code]

As you can see, I haven't included any code for executing a query, but I don't think that will pose a huge problem.

Anyway, if someone could help me out or point me in the correct direction, and perhaps give me an example of how a class like this would be used (spesifically the opening of a database connection) I would be very very grateful :)

-Kellendil

[trq]

So let me get this straight. Youve made a class but don't know how to use it? Firstly... you really dont need the sqlOpen function to return anything, just have it set a private connection variable that can then be used within the class.

Really, the class itself should take care of instigating connections too, you shouldn't need to specifically call a method to open a connection.

Basically, all the code in your example isn't really needed (or wanted) within a database class.

[kellendil]

As I said, it was a feeble attempt, I know that it isn't correct, which is why I'm asking for help :]

[quote]Really, the class itself should take care of instigating connections too, you shouldn't need to specifically call a method to open a connection.[/quote]

This is what I've read elsewhere as well, but I haven't been able to find a good example, so I don't really understand how I do it.
[quote]Basically, all the code in your example isn't really needed (or wanted) within a database class.[/quote]

How does one close a database connection then (manually, I know that it isn't usually necessary)

-Kellendil

[CheesierAngel]

You should code your class on a different approach:

What should this class do ?
- Create a connection
- Execute queries with the made connection
- Close your connection if asked.
What shouldn't this class do?
- Error handling !!!
- Configuration !!!

[code]
<?php
require_once('dbConfiguration.inc.php');

class database {
  private $config = $GLOBALS['dbConfig'];
  private $db = null;
  public $errorMessage = null;
 
  function database($dbName) {
    $this->db = mysql_connect($this->config['dbHost'], $this->config['dbUser'], $this->config['dbPassword'])
    or $this->errorMessage = mysql_error();
    if($this->db) {
      mysql_select_db($dbName, $this->db) or $this->errorMessage = mysql_error();
    }
  }

  function sqlClose() {
  mysql_close($this->db)or $this->errorMessage = mysql_error();
  }

  function sqlQuery($query) {
    $results = null;
    $results = mysql_query($query, $this->db) or $this->errorMessage = mysql_error();
    return $results;
  }

  function getErrorMessage() {
    return $errorMessage;
  }
}
?>


How to use this class:
<?php
require_once('database.class.php');

$db = new database('DatabaseName');  // Makes connection
// Your script that uses the class chooses whatever to do with the generated errors !!!
if($error = $db->getErrorMessage()) {
  exit($error);
}

$query = "SELECT * FROM table";
if(!$results = $db->sqlQuery($query)) {
// Again: Your script that uses the class chooses whatever to do with the generated errors !!!
exit($db->getErrorMessage());
}

if(!$db->sqlClose()) {
  // And again: Your script that uses the class chooses whatever to do with the generated errors !!!
exit($db->getErrorMessage());
}

/*
This script does not wanna know how the connection is made, does not wanna know the db connection link !!!
This script handles the database errors output !!!
....
*/

?>
[/code]

[kellendil]

Thanks alot, lets see if I understand it all :>

[code]require_once('dbConfiguration.inc.php');[/code] ok, this is where i put my configuration, in your example it would look something like this?
[code]
<?php
//configuration file for databaseconnection.
$dbconfig['dbHost'] = 'databasehost';
$dbconfig['dbUser'] = 'databaseusername';
$dbconfig['dbPassword'] = 'databasepass'; 
?>
[/code]

The rest of the code is pretty self explanatory, so I won't ask stupid questions about that :]

You are absolutely correct about seperating the errorhandling and configuration, I should have though about that myself, but as I mentioned, I'm fairly new to the OO approach :)

Thanks again for your help :)

-Kellendil

[CheesierAngel]

The idee to seperate your error handling from all other classes is to create a class specially for this.
Now you could make a class errors or something like that that will keep all your generated errors into
a database (by using your database class) or error log file. And on every page of your application/site
you could aks the errorClass the latest error to display if any new errors where added.

something like:
[code]
<?php
require_once('error.class.php');
require_once('database.class.php');

$cError = new Error();
$cDatabase = new Database();

$cDatabase = new Database('databaseName');
if($error = $cDatabase->getErrorMessage()) {
$cError->add(ERROR_CRITICAL, $error);
}
?>
[/code]

And you could add in your pages header or footer:
[code]
<?php
if($cError->newError()) {
  $echo "<font color='red'>" . $cError->lastError() . "</font>";
}
?>
[/code]

And indeed in your dbConfiguration.inc.php you put all your configurations.

You should know that programming OO is to extract all specific functionalities into an object/class and only these specific functionalities. So if you create a database class you should only create the functionalities that concern databases into this class. And so on ...

[kellendil]

thank you, you have been very helpful :)