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A child class will perform all the same functions and utilize the same properties as the parent class. Additionally, a child may add its own attributes and abilities.
Remember that the parent class will NOT know about any properties or methods added to the child.
Documentation
- strip_tags() - Strip HTML and PHP tags from a string. You can use the optional second parameter to specify tags which should not be stripped.
- trim() - Strip whitespace (or other characters) from the beginning and end of a string
- get_class() - Returns the name of the class of an object
- is_a() - Checks if the object is of this class or has this class as one of its parents
Other Option
Additional Features You Could "extend" a Listing
- logo
- dates
- code of conduct
- call for papers
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As a child of listening basic,
the listing premium class will perform
0:00
all the same functions and utilize
the same properties as the parent class.
0:04
Additionally a child may add it's
own attributes and abilities.
0:09
This is where extending comes in.
0:14
There are many additional features that we
could add to extend the premium listing,
0:16
such as a description, logo, dates,
code of conduct and call for papers.
0:22
For this project I’m going to add
a description, but go ahead and
0:27
add your own features when we’re done.
0:31
The first thing we need to do is create
a new property with it's getters and
0:34
setters.
0:37
Private $description;.
0:38
Let's copy the title getter and
setters from the ListingBasic class.
0:43
Now we can replace title with description.
0:55
Let's test this out on our index page.
1:10
We'll add a new object named test, and
we'll set this = new ListingPremium().
1:16
Now let's move our display out of the for
each loop.
1:25
Now we can add a description
to the test on the index page.
1:35
We'll set this to My description.
1:42
Now, let's check this out in the browser.
1:49
Whoops, I forgot to
change listing to test.
1:53
Let's try that again.
2:03
Great, our test listing has
the new description property.
2:07
Let's add a little more.
2:12
I want to allow my description
to accept certain tags.
2:14
There are many different ways to do this,
but
2:17
I'm going to use the strip tags function.
2:19
So let's check out the documentation.
2:21
You can use the optional second
parameter to specify tags,
2:31
which should not be stripped.
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You specify a string with a simple
form of the tags you wish to allow.
2:38
Let's create a new protected property.
2:43
Protected $allowed_tags,
2:48
and we'll set this to
2:54
for
2:58
emphasis,
3:05
That will give us a decent list.
3:12
Now we need to change the setter.
3:20
We've been using the filter_var to
sanitize the information coming in.
3:23
This allows us to safely accept user data.
3:27
Instead of filter_var,
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we're going to use the strip_tags function
to strip all but a few simple tags.
3:31
For the second parameter,
3:42
we specify our allowed
tags $this->allowed_tags.
3:45
Let's go back to index.php, and
add some tags to our description.
3:52
Good tags, and-
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Bad tags.
4:20
Now, let's test this in a browser again.
4:25
You can see that the description left
the B tags but removed the link.
4:33
Because the A tag is not
one of the allowed tags.
4:37
Remember, the set description method is
specific to our listing premium class and
4:41
our listing basic class
will not be affected.
4:46
Let's try changing this test
to use our ListingBasic class.
4:49
Now we get a call to undefined
method on our ListingBasics class,
5:01
because it does not know about
the set description method that
5:05
only applies to a listing premium object.
5:09
Let's change this back to listing premium.
5:13
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