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We have the code required to retrieve
the item information from the database.

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It's time to use those results
to display our media items.

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Unfortunately, changing the site to use
a database instead of a simple array

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is going to require us to
rewrite everything from scratch.

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Gotcha, actually it's not,

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the original data.php file contains
an array of catalog information.

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All we need to do is update that file

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to pull the catalog information
from the database instead.

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After that we can start
updating our functions to make

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better use of the data from the database.

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In the functions file we have the code for

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manipulating the catalog information and
adding it to our site.

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The data.php file
contains the data itself.

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This is an example of the programming
concept known as separating concerns.

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As you do more programming,
you'll hear more and

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more about the concept
of separating concerns.

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One of the main benefits of separating
concerns is that you can make

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major changes in one area, without
having any effect on the other areas.

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For our listing pages,
we separate our concerns so

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that all we have to
change is our data file.

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>> Back in the workspace associated
with this video, let's change data.php.

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By changing this file we won't have to
rewrite any of the path to our includes.

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Will include the connection.php file and

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then we'll comment out
the rest of this code.

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This will leave it here for reference.

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Now let's go back to connection.php.

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Our code creates a pdo object
that connects to the database.

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It runs a query against that database and

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displays the result set as
an array to the screen.

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Let's change this last line, so
that instead of displaying the results

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to the screen it loads it into
a variable called catalog.

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The original array of catalog information,

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was also stored in
a variable name catalog.

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So by storing the results of our
database query in the same variable

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our original code will still work.

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Now let's go take a look at the home page.

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It looks exactly as it did, which is good.

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We haven't made any changes
to the function of the code.

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All we're doing is generating the catalog
array from the database using pdo.

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If I click on Books in the navigation,
we'll see our Books page, Movies,

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Music and our Full Catalog.

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All of those pages currently
call functions that in turn

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use the catalog array.

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We were able to change the source of
the data displayed on these pages

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by simply putting the results of our
database query into a catalog array,

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instead of recreating that array manually.

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Just to make sure that
we're using the database,

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let's change our connection
string to break the connection.

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If our code is working properly,
this will show an error message.

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This looks right.

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Our site is using our code that
connects to the database and

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when the string is wrong,
we're getting the error message.

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Let's change that back.

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And everything looks good.

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>> Before we move on.

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I want to point out that we will
be improving the performance

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on some of these pages shortly.

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Currently our code retrieves
all the items in the catalog.

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This makes our code do
extra unnecessary work.

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For example to display only
the books in the catalog.

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The code retrieves the entire catalog,
books, music and movies,

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then loops through the entire
catalog to display just the books.

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This type of filtering is the type
of work at which databases excel.

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We'll eventually write additional queries
to make our database handle that load.

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And in turn, this makes our site faster.

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Before we're done with this project, we're
going to set up multiple functions and

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multiple queries to the database
to pull specific data,

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instead of the entire catalog.

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But before we do that,

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let's modify the code we just pasted to
make things cleaner and easier to reuse.