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Our catalog page needs to display different categories depending on what the user selects. In this video, we’ll start talking about some special server variables and conditionals necessary to switch categories.
Update to html
index.php unordered list for our random items should have a class of "items".
<ul class="items">
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Right now all our media categories
link to the same catalog.php page.
0:00
We want to be able to specify which
category the catalog should display.
0:05
We can accomplish that by adding
a string at the end of the URL.
0:11
After the file name, type a question mark,
and a variable with any name.
0:14
Let's call it cat, short for category.
0:18
We use an equal sign, and
then specify a value of books.
0:21
Variables added to the URL in this
manner get sent to the server,
0:26
along with the request for the webpage.
0:30
They are available in a special
php variable called _GET,
0:32
all uppercase, and
our element cat in square brackets.
0:36
The element cat is the same name
we gave our variable in the URL.
0:42
We can use this value in a conditional to
check which category should be displayed.
0:46
There are four options for this page.
0:52
Our three categories, books, movies,
and music, and the full catalog.
0:54
We want to check if the get variable cat
0:59
is set to one of these
three specific categories.
1:02
And if not, show the full catalog.
1:05
Now it is possible to type anything
after cat equals in our address bar, so
1:08
we want to make sure that we are only
looking for one of the 3 categories.
1:13
We're going to edit our catalog.php file.
1:18
The page title with the value
Full Catalog will be our default.
1:21
A default is used if none
of the conditions are met.
1:26
In other words, if there's no variable set
for the cat variable in the query string,
1:28
we'll display the full catalog, all the
books, movies, and music in the library.
1:34
So let's write a conditional right after
our page title that checks the value of
1:39
the get variable cat.
1:43
If, $_GET["cat"]
1:47
double equals, "books".
1:52
We want to set our
$pageTitle equal "books".
1:58
To check for our other two categories we
can add an else statement with another if.
2:05
Else, if, $_GET["cat"]
2:09
double equals movies
2:13
We'll set our $pageTtitle = "Movies".
2:25
Finally, else if
2:33
($_GET["cat"] == "music").
2:37
We'll set our $pageTitle = "Music".
2:45
Close out our conditional.
2:53
To make this a little easier to
see when we click the links,
2:55
we're going to set the H1 tag
to use our page title as well.
2:57
Open php echo $pageTitle.
3:00
Close php and save.
3:06
Now, we need to change your
navigation to use these values.
3:09
Open header.php and
add our query string after catalog
3:12
?cat=books and for
3:18
movies we'll do ?cat=movies.
3:23
For music, ?cat=music.
3:28
Again, we can see that having
an include file makes it so
3:35
much easier to make changes to our header.
3:38
Now when we go back into the browser.
3:40
And we refresh our page.
3:43
Our navigation will pass
the correct variables.
3:45
Books, movies, music.
3:49
And the title is displayed on the page
based on what category we're in.
3:52
One last thing we should
do in this conditional.
3:57
We're currently checking the value
of the get variable cat here.
3:59
But, if the variable doesn't exist at all,
4:02
then this conditional
would generate a notice.
4:05
Let me show you.
4:07
Let's remove the cat equals music.
4:09
Yuck.
4:14
Not something we wanna see.
4:15
Let's fix that.
4:16
Let's go back into work spaces,
and our catalog file.
4:18
Before this conditional,
we need to do another check.
4:22
We're going to use php's isset function.
4:26
If (isset ($_GET["cat"]
4:29
Then move on to execute.
4:42
Is conditional.
4:43
Now when we save this file and
go back into our browser,
4:49
we refresh the page and we see our full
catalog, books, movies, and music.
4:53
We still need to actually
display the full catalog or
5:01
the categories which we'll
do a little later on.
5:03
We have everything in place to
choose the category we want to show.
5:06
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