PHP OOP

Asked by: krydea

Hello,

I have created an interface with the following methods:
newInstance()
setResultSet($rs)
etc.

I implemented the interface in three different classes: county, region and district.

I created a new class Container that implements an iterator and that contains an array of county, region or district. Now the problem is that I want to call the implementation dependent methods from: county, region or district and at some point I want to get one of the elements from the container.

My code gives me the error: Call to a member function getTableName() on a non-object;
I though the following should work, but it doesn't:

$cont = new Container(new County());
$rs = (County) Container.get($key); 
 
with the class set up like:
class Container{
	private $dataTypeClass;
	private $Container=array();
	
	 public function __construct($dataType){
		$dataTypeClass = $dataType; 
	}
	
	public function get($key) {
		$this->dataTypeClass->getTableName();
		$fields = $this->dataTypeClass->queryFields();
		$tableName = $this->dataTypeClass->getTableName();
		$sqlSelect ="SELECT $fields FROM $tableName WHERE id=='$key'";
		$rs = db->doSelect($sqlSelect);
		$this->dataTypeClass->newInstance(); //clears the dataTypeClass
		$this->dataTypeClass->setResultSet(rs);
 
	return $this->dataTypeClass;	
	}
}

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I realise that there is another error in your code:
Container.get($key);
Instead use:
$cont->get($key);

This would also give an error (probably the one you reported above):
Container::get($key);

The way that you are doing that is probably the most generic way. You could subclass the container class and make the County class extend the Container class. Use parent::get($key) if you also have a get() method in your County class. This would mean that a similar thing could be achieved with $rs = new County()->get($key).

Here are some tips that you may find helpful:

For mysql __destruct() is useful for closing the mysql connection and/or (more importantly) $mysqliResult->free_result().
In OOP with PHP it is useful to use the mysqli extension instead of mysql and $mysqliResult->fetch_object()
Sometimes it is useful to use $miscObject = new StdClass(). This will give you an empty object that you can use like $miscObject->public_var = 'whatever'.

Also, so that you know coming from Java, (County) - type casting - is not required in PHP.
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