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Extending Object-Oriented PHP

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Using Multiple Classes

3:13 with Alena Holligan

When using multiple classes, there are several functions in PHP that will allow us to learn about those classes.

In the last video, we saw that we could easily swap out our new child class, 0:00
where we use the parent. 0:04
Let's take a closer look at the result. 0:06
Open index.php. We'll start by adding a var_dump of 0:08
the listings within the foreach loop. 0:12
Let's preview this in the browser. 0:20
Lets view the page source, and increase the font size. 0:25
This shows us that the object itself is a listing premium object, but 0:29
its variables are taken from the listing basics class. 0:36
Let's take a look at a couple more functions that will tell us about 0:45
our class. 0:48
Var_dump get_class, 0:53
This will give us the name of the object's class. 1:03
We can also check if this object is of a certain type. 1:06
We'll do a var_dump is_a, pass the listing, 1:09
And then the class we wish to compare, ListingBasic. 1:18
Let's preview this again. 1:24
Now we see that it tells us that our class is a listing premium, but 1:28
our check with the is a function, returns true. 1:32
That's because listing premium is a child, and therefore a type of 1:36
ListingBasic, and can be used wherever ListingBasic is used. 1:41
We could also see in the status of these listings, 1:46
that some of them are premium, And some of them are basic. 1:48
Let's go back to our collection class and use ListingBasic for 1:55
our basic listings, and ListingPremium for our premium listings. 1:59
In the addListing method, we need to check the status. 2:08
If isset status, 2:16
And that same status, 2:23
Is equal to premium, then we're going to use ListingPremium. 2:31
If not, else, we're going to use listingBasic. 2:38
Let's check this out in the browser once more. 2:51
Now the listings that have a status of basic, are of a ListingBasic class. 2:55
And those that have a status of premium, are of a ListingPremium class. 3:03
We're ready to actually extend our child class in more than just name 3:08