Share a parameters class with other classes - php

Question

I would like to share the parameters taken from a table in a db.
To take these parameters, I created a class made ​​for this.
this is my scenario to share the parameters contained in a db between the various classes. is the correct approach to do this?
class Database
{
$private mys;
public function __construct()
{
$this->mys = new mysqli(....);
}
}
class params
{
$private db;
$public var1;
$public var2;
public function __construct()
{
$this->db = new Database();
}
public function getParams()
{
$result = $this->db->mys->query ("SELECT * FROM params");
while($row = $result->fetch_assoc())
{
$this->var1 = $row['var1'];
$this->var2 = $row['var2'];
}
}
}
class foo
{
private $db;
private $ps;
public function __construct()
{
$this->db = new Database;
$this->ps = new Params;
}
public function viewParams()
{
echo $this->ps->var1;
echo $this->ps->var2;
}
}

Answer 1

To access the private fields from other classes declare public 'getter' methods like:
public getVal1() {
return $this->val1;
}

Answer 2

In my modest opinion, there are various ways to share a parameters class with other classes. And they depends on how your system currently is and how it'll grow.
From what I learnt, a correct ways to pass dependencies to your classes is to inject they to the constructor, ex instead of:
class foo
{
...
public function __construct()
{
$this->db = new Database;
I would prefer to instanciate $db first:
$db = new Database();
and then
class foo
{
...
public function __construct(Database $db)
{
$this->db = $db;
This way your classes are loosely coupled and you can afford Unit Testing easily one day, working with interfaces and not concrete implementations, etc...please take a look at http://en.wikipedia.org/wiki/Dependency_injection
As a personal suggest I'll try to design the params class as an entity, mapped as a Db table object:
//entityParams.php
class EntityParams
{
private $id; //column name
private $columnA;
private $columnB;
public function setId($id)
{
$this->id = $id;
}
public function setColumnA($columnA)
{
$this->columnA = $columnA;
}
...
}
then use a Database class as a simple connector class (just to promotes single-responsibility and separation of concerns):
//Database.php
class Database
{
private $dbh = NULL;
public function connect()
{
$this->dbh = new Mysqli(...);
}
public function getConnection()
{
if(is_null($this->dbh))
{
$this->connect();
}
return $this->dbh;
}
}
and use a DatabaseManager instead, to let it do all dirty works.Something like:
//DatabaseManager.php
class DatabaseManager
{
private $db;
private $entities = array();
private $currentEntity;
public function __construct(Database $db)
{
$this->db = $db;
}
public function fromEntity($entityName)
{
$entityClass = "Entity".ucfirst($entityName);
if(!isset($this->entities[$entityClass]))
{
$this->entities[$entityClass] = $entityName;
}
$this->currentEntity = $entityClass;
return $this;
}
public function getAll()
{
$results = $this->db->getConnection()->query("SELECT * FROM {$this->entities[$this->currentEntity]}");
$entities = array();
foreach ($results->fetch_all(MYSQLI_ASSOC) as $key => $item)
{
$e = new $this->currentEntity;
$e->setId($item['id']);
$e->setColumnA($item['columnA']);
$e->setColumnB($item['columnB']);
$entities[] = $e;
}
return $entities;
}
Finally your Foo class (and everyone else) just has a simple dependency with the DatabaseManager (which could evolve as a RespositoryManager):
//Foo.php
class Foo
{
public $dbm;
public function __construct(DatabaseManager $dbm)
{
$this->dbm = $dbm;
}
public function viewParams()
{
return $this->dbm->fromEntity("params")->getAll();
}
public function viewParam($id)
{
return $this->dbm->fromEntity("params")->find(2);
}
}
//client.php
/* Here you can instantiate the classes and pass they through constructor or investigate on how to create and use a Dependency Injection Container */
$db = new Database();
$dbm = new DatabaseManager($db);
$foo = new Foo($dbm);
var_dump($foo->viewParams());
var_dump($foo->viewParam(1));
I just wrote simple basic ideas that could be worth to play around it and improve it.