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To inherit ALL the abilities and attributes of another class, we use the keyword "extends ".
Key Concepts
- Use the Keyword extends
- You can only extend from one class at a time.
- A child class will "inherit" all the attributes and actions of a parent
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Let's jump right into code and
see what it takes to extend a class.
0:00
The classes for this project
are stored in a folder named classes.
0:04
In that folder is a listing
ListingBasic class.
0:08
This is the class we're going to extend.
0:11
So let's take a look at
what the class includes.
0:13
There are some private properties,
a constructor that sets those properties,
0:18
and the getters and setters for
each of those properties.
0:23
There's also a method named two array
0:25
that turns the object properties
into an associative array.
0:28
Let's create our new class
in the classes folder.
0:32
We'll name it ListingPremium.
0:37
To build a class, we use the keyword
class, followed by the name of our class.
0:47
To inherit the abilities and
0:53
attributes of another class,
we then use the keyword extends.
0:55
Followed by the name of the class
we wish to extend, ListingBasic.
1:01
We'll add the curly braces but
leave this new class empty.
1:07
Before we do anything else let's
try using this new child class.
1:12
Open classes Collection.php.
1:17
This is the main controller for
our application.
1:20
This class takes a connection
to a database on construction.
1:23
It also has a method for
selecting listings from the database.
1:27
This method calls the addListing method,
that adds a listing and
1:32
returns a listing object.
1:37
For right now, all we're going
to do is change the class used.
1:40
From ListingBasic to ListingPremium.
1:44
Before this will work I need to make this
new class available to the application.
1:50
Open inc, config, this file performs some
of the basic tasks for our application.
1:54
We start a session Include the classes,
connect to the database, and finally,
2:03
create a directory object by passing
the connection to our collection class.
2:08
Lets copy the listing basic include.
2:13
And we'll change it to ListingPremium.
2:19
Now lets preview this site in a browser.
2:25
Even though we didn't add any code
to our ListingPremium's class,
2:29
the site still functions exactly the same.
2:34
Let's go back to our ListingPremium class.
2:37
As you can see, this is in fact empty.
2:43
However, we use the extend keyword
to extend from ListingBasic.
2:47
ListingBasic is the parent class and
ListingPremium is the child class
2:53
that inherits all the abilities and
attributes of the parent.
2:58
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