treating an object like a hash (as in perl)

[compbry15]

Hello all,

I recently began a project that must be done in PHP, due to server constraints (no mod_perl). I have a lot of experience with perl, and am used to being coddled by some of the magic you can perform therein. 🙂

One particular situation I was hoping I could get clarification on is, for lack of a better expression, treating an object like a hash.

In perl we could have something like the following:

Inside SomeObject.pm:

# Just some random functions
function foo {}
function bar {
   my $self = shift;  # like the $this variable, i'd say.

   $self->{SomeValue} = 'test';
} 

function baz {
   my $self = shift;

   print $self->{SomeValue};
}

Inside SomeOtherObject.pm:

function foobar {
   my $someobject = new SomeObject;

   $someobject->{Test} = 1;

print $someobject->{Test};
}

As you can see, whether inside the object, or using it from another location, you can treat an object like a hash and add values onto it on a whim. They persist through the life of the object, until destroyed.

Now, in Perl that is all fine and dandy to do ... Perl doesn't have a very stringent object-oriented structure (compared to other languages).

My question is two-fold. In PHP, is this possible? And if possible, is it considered bad programming practice to handle variables in only this way (i.e. never officially declaring object variables ... although I would declare temporary function-level variables normally).

Hopefully that made sense, I have tried phrasing it various ways into google with no success.

Thanks in advance for any help or information.

[NogDog]

Yes, you can add undeclared object variables to an object, e.g.:

<?php
class Test
{
   public $foo = 1;
}

$test = new Test();
$test->foo = 11;
$test->bar = 22;
echo "<pre>".print_r($test, 1)."</pre>";
?>

The above will output:

Test Object
(
    [foo] => 11
    [bar] => 22
)

I don't think I've ever felt a need to do such a thing, though. Normally, if I want to be able to track some indeterminate list of things within an object, I use an array within the class for it, e.g.:
[FONT="Courier New"]$test->someArray['foo'] = 'bar';[/FONT]

But I don not know of any specific technical reason why you should or should not do it either way, it just "feels" wrong to me to add undeclared variables to an object. 🙂

[compbry15]

Thanks for the quick response 🙂

Yes, I can see how it may feel wrong coming from an OO standpoint. However, coming from perl it just feels annoying to do it the other way hehe 🙂

For instance, I have a bunch of DB Records (Tables), and each one has Record.php, with some functions that always are called on all types of records (i.e. saving, etc).

In perl, at least in my company's system, when a new object is instantiated, the constructor automatically fetches all the info for that record from the DB and loads it into the hash.

So if we have a Person, we create the new Person object, then can do things like $person->{FirstName}, etc etc. This is really nice because for some of our clients we are constantly adding new fields to our different class types. So, when we add a new field to the actual DB record, and the object is created, that new field will automatically be available ... If we didnt do this, every time we create a new field in the DB, we would have to add a new variable declaration.

Hopefully that explanation makes sense as to why I am used to doing it this way. However, now that I think about it, it is probably equally easy to have the constructor load the values from the DB into some array for later use and just access it like $person->data['FirstName']

While I was waiting for a reply, I actually stumbled upon the set and get magic functions. Is it not required to declare these with the example you stated above, or do they just provide the ability to expand on this basic premise with more details/functions?

[NogDog]

Yes, you could use get() and set, perhaps even with the array thing:

<?php
class Test
{
   protected $data = array();

   public function __get($key)
   {
      return (isset($this->data[$key])) ? $this->data[$key] : null;
   }

   public function __set($key, $value)
   {
      $this->data[$key] = $value;
   }
}

$test = new Test();
$test->foo = 'bar';
echo $test->foo;  // outputs 'bar'
echo "<pre>".print_r($test,1)."</pre>";
/*
outputs:

Test Object
(
    [data:protected] => Array
        (
            [foo] => bar
        )

)
*/
?>