Is there a correct way to build a PHP/MySQL Class?

[jont]

The subject says it all really but to explain a little better here's what I mean.

 

At the moment I've made a separate class for each type of query and one for the actual database connection so I have the following classes: dbConnect, dbSelect, dbInsert, dbUpdate and dbDelete.

 

I'll use my dbSelect class as an example of how im doing things currently.

 

Here's the dbSelect class, I've removed some non-important bits just to make it a bit shorter to post on here

function __construct($tables='', $columns='') 
{
$this->tables = $tables;
$this->columns = $columns;
$this->query = "SELECT $this->columns FROM $this->tables";
}

public function select()
{

if($this->where != '')
{ 
	$whereCount = count($this->where);
	$x = 0;
	foreach ($this->where as $column => $value)
	{
		$x++;
		$this->whereQuery .= $column . ' = \'' . $value . '\'';
		if($x!=$whereCount) $this->whereQuery . = ', ';
	}
	$this->query = $this->query . ' WHERE ' . $this->whereQuery; 
}

if ($this->order != '')
{ $this->query = $this->query . ' ORDER BY ' . $this->order;}

if ($this->limit != '')
{ $this->query = $this->query . ' LIMIT ' . $this->limit;}

$doQuery = mysql_query($this->query);
$row_count = '0';

$results = array();

while($row = mysql_fetch_assoc($doQuery))
{
	$row_count++;
	$results[$row_count] = $row;
}
$this->results = $results;
}

 

and this is an example of how im performing select querys

$selectSomething = new dbSelect("table_name","columns");
$selectSomething->where = array('column_name' => 'column value');
$selectSomething->limit = '1';
$selectSomething->select();

 

So basicly I'm creating a new object for every query, which for me works fine but I've got a feeling its all wrong.

 

I've only just started working with classes so I could be going about this completely wrong but i don't seem to be having any problems with it.

Have I gone about this completely the wrong way or is there a better/faster way of doing it?

 

[abazoskib]

You do not want to create a new object for every query. That is completely not the point of creating a class. Why odn't you create a class for a database object(connection and picking which database you want to use), then create methods within that class to perform different queries, and such. It's a hefty task to get all the functionality in there. You might want to check out sample code thats already been written. Don't reinvent the wheel.

[ignace]

Actually that idea is not so bad but I would change it a bit:

 

class SQLInsert {
    public function into($table) {
        return $this; // used for method chaining.
    }
    public function values($data) {
        return $this;
    }
}

$insert = new SQLInsert();
$insert->into('table')->values(array('id' => ..))->values(array('id' => ..))..

[jont]

are there any disadvantages of using the way I've done it, with some changes like suggested?