Posted on 2009-05-16
Last Modified: 2013-12-12

I have created an interface with the following methods:

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) {
		$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
	return $this->dataTypeClass;	

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Question by:krydea
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Expert Comment

ID: 24402126
                $dataTypeClass = $dataType;
                $this->dataTypeClass = $dataType;
and it should work.


Author Comment

ID: 24402173
Damn that's all:p I just started PHP. Java has generic classes. Does PHP support a nicer way to do stuff this?

Accepted Solution

pedro_sland earned 250 total points
ID: 24402426
I realise that there is another error in your code:
Instead use:

This would also give an error (probably the one you reported above):

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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LVL 34

Expert Comment

by:Beverley Portlock
ID: 24402435
It is nothing to do with generic classes. Inside a PHP class you MUST use the $this-> syntax to reference class properties and methods.

Expert Comment

ID: 24402436
I don't know why I have html above as I didn't type it. Please edit.
LVL 34

Expert Comment

by:Beverley Portlock
ID: 24402517
pedro - using the rich text option on the editor is what did it. If you are going to include HTML it is best to stick to plain text.

I had a hilarious time some months back when I posted the HTML for a form in Rich Text .....

Author Closing Comment

ID: 31582196

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