Data models in php

Question

I'm sort of experimenting with very obscure data models in php. For example, if I have a table called "model_attributes" in an SQL database. This is a list of all the available attributes for the model I'm working on. Now, I want the model, and other models to be able to derive functions from this list to pull data out of an array, after the data has been loaded into the array from the constructor. Here is an example in pseudo-code:

for each attributes as attribute
    create new function ( getAttributeName )

and

getAttributeName() 

would

return $this->_model_data['attribute_name'] 

First off, is this good practice? It seems organized, but at the same time seems kind of dirty. Maybe someone could give me some other suggestions as to how to handle large data models in php.

Also, if anyone has done something like this, how could I handle this in phpDocs?

Answer 1

You will not be able to do this easily at runtime with PHP.

You may use an existing ORM, for example Doctrine or Propel.

Or you could pre-generate the model class files, or use magic methods.

Quick example:

class something {

    private $_model_data;

    public function __call($name, $value = null) {
        if (strpos($name, 'get') === 0) {
            $attribute = substr($name, 3);
            return $this->_model_data[$attribute];
        } else if (strpos($name, 'set') === 0) {
            $attribute = substr($name, 3);
            $this->_model_data[$attribute] = $value;
        }
    }
}

__call is a magic method that gets called when the method does not exists. So, calling getAttributeName on an instance of the class would call __call with the string getAttributeName as first argument.

Answer 2

If you just want to access the array of model_data from the context of a container object, you should use either the __get magic method, or implement the ArrayAccess interface.

__get is the easy way out as the implementation would look something like this:

function __get($name)
{
  if (array_key_exists($name, $this->model_data))
  {
    return $this->model_data[$name];
  }
  return;
}

To access the data you'd just call the property of the object: $obj->property_name, or in the case where you're using a string: $obj->{$property} Of course, this may interfere with any public attributes you have (generally a bad idea to have them anyway).

Alternatively you can set up your object as an implementation of ArrayAccess, which will allow you to access the property as: $obj['property_name'], or $obj[$property]

Both solutions will allow you to have custom access management, if you want to obfuscate your field names, or adjust how the data is retrieved later.

AFAIK the ArrayAccess method is faster, but you'd have to test it to be certain. Magic methods have a tendency to be a bit slow.