Re: accessing variables within objects

On Jul 31, 2008, at 1:49 PM, Jim Lucas wrote:

Philip Thompson wrote:

On Jul 30, 2008, at 1:29 PM, Jim Lucas wrote:

Marten Lehmann wrote:

Hello, I'm using some php-classes which worked fine with php-5.0.4. Now I tried to upgrade to php-5.2.6, but the classes give a lot of errors. If I set error_reporting(E_ALL); I see messages like Notice: Undefined property: FastTemplate::$main in /whereever/inc.template.php on line 293 Notice: Undefined property: current_session::$cust_id in /whereever/inc.init.php on line 117 In inc.template.php there are a lot of calls like $this->$key. In inc.init.php there are calls like $session->cust_id.

to fix these errors, you would need to modify the code so it does something like this. where it calls $this->$key you need to check and make sure that $key exists before you trying call for it. So something like this would work. if ( isset( $this->$key ) ) { $this->$key; } else { $this->$key = null; } You didn't show any context in which you are using the above code. So I don't know what will actually work in your situation. Show a little more code that includes the method in which $this->$key is called. You will want to look at using the Overloading feature of PHP5. Check out this page for overloading examples http://us2.php.net/manual/en/language.oop5.overloading.php Take note of the __get() and __set() methods. The __get method checks to see if the key exists before it tries working with it.

Ok, I'm trying to understand the point to using these overloading methods. <?php $obj = new ClassThatUsesOverloading (); $obj->hi = 'Hi'; $obj->bye = 'Bye'; echo $obj->hi, ' ', $obj->bye; // Output: Hi Bye ?>

I was only suggesting the overloading because it would be the simplest thing to implement in an existing class without massively re-write parts of your application. You could simply add the __get() method and then have it check to see if the value or $key existed before it tries using it. And if it doesn't exist, then return null or something else. This would get rid of a lot of your NOTICEs from PHP. I would add a method something like the following to your class and it should fix the problems with trying to access properties that do not exist. function __get($key) { // Check for the existence of the key in object if ( isset( $this->$key ) { // If found, return value return $this->$key; } // Default: return null return null; }

You could have done that or you could do the following..... <?php $obj = new ClassThatDoesntUseOverloading (); $obj->setHi('Hello'); $obj->setBye('Bye Bye!'); echo $obj->hi(), ' ', $obj->bye(); // Output: Hello Bye Bye! ?>

This example is flawed by the fact that you are call hi and bye as a method instead of referencing the property.

Wait a second. Isn't that the point of encapsulation and abstraction? You don't have direct access to properties - only the class does (well, if it's private). ~Phil

The 2nd way seems more *OOP* than the first - weird to explain. I guess what I'm wanting to know is.... why would you use overloading (in PHP)? The only reason I can think of is to avoid having to create/use accessors. Please help me understand! But please be nice! =D Thanks, ~Philip

What has changed in php-5.2.x so that these calls don't work any more? What is the new, required form to use objects in a similar manner (unfortunately I have no ressources to code these classes from scratch)? Thanks. Kind regards Marten