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Don't Repeat Yourself
3:35The DRY Principle is one of the tenets or key concepts of programing. DRY (D-R-Y) stands for Don't Repeat Yourself. If you see yourself repeating code in the same place, for example, writing the same string over and over again, it's a good sign you can improve your programming using DRY programming techniques.
Now that we know how to
process a PHP file on the web,
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let's start putting PHP to good use.
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Remember, variables
are a way to store data.
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One reason to store data in a variable
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is to use that data in
multiple places in your code.
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This will also allow us to change
the data in one place while
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affecting every line of code
in which that data is used.
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This is one of the tenets, or
key concepts, of programming.
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It's called the dry principle.
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Dry, D-R-Y, stands for
don't repeat yourself.
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If you see yourself repeating code, for
example writing the same string over and
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over again, It's a good sign that
you can improve your programming
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by using DRY programming techniques.
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Let's go back to Workspaces and take
a look at how to use the variables and
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the DRY programming principles in
the name we've been using for our page.
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In the last video,
I set up code block and echoed my name.
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Let's see how we can make this program
more flexible using a variable.
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Instead of echoing out this string, let's
change this to a variable display name.
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Before we can use the display name
variable we have to give it a value.
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Let's set the value for
display name at the top of our file so
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that we can use this anywhere.
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Before the opening HTML tags,
and even before this doc type.
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let's add a new PHP block.
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Then we can set our variable
display name equal to my name.
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We can add as many code blocks
as we want throughout our page.
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Now we can save this file and
refresh the browser.
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We see that nothing has changed but
that's good it's working just as before.
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Now let me show you why variables are so
useful.
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Let's use this display name
variable in a few different places.
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Let's copy this whole code block.
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And up in the title,
instead of saying PHP Basics at Treehouse,
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let's change this to
PHP Basics by Alena Holligan.
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Using our display name.
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Let's add this in one more place,
the copyright in the footer.
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Instead of saying Copyright
2016 Treehouse Island Inc,
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let's say Copyright 2016 Alena Holligan
using our display name variable.
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We'll replace Treehouse Island Inc
with our display name variable.
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Now let's save the file and
refresh the browser.
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Now I have Alena Holligan in three places,
the title, the left bar, and the footer.
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That makes this a little more useful.
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But now what happens if I want to
change the way my name is displayed?
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Let's go back to work spaces and
the first code block at the very top.
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Instead of saying Alena Holligan let's
change this to Alena A Holligan.
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We'll save the file and
refresh the browser.
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Now everywhere that uses the display name
variable is updated to this new value.
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You're doing a fantastic job
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learning foundational programming concepts
and building your first PHP driven page.
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By storing and
retrieving information in a variable,
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we are able to quickly update our
page when requirements change.
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Wouldn't it be nice to have changes update
without us having to change anything?
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Okay so this isn't always possible but
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there are some things that we can
set up and let PHP do all the work.
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