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Let's continue to work on our
module from the last video.

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If we go to our form on the website,
fill it out,

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and click the submit button,
the page just reloads.

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Nothing actually happens
with the form data.

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That's because we haven't told the module
what to do with that form submission.

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Let's do that by hooking into
the form submission event.

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It's called hook_form_submit.

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We'll implement it by adding a function
to our summed up module file named

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after the hook, replacing the word
hook with the name of our module.

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Followed by the rest of the name of
the hook, giving us, sum_form_submit.

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I'll add in the function keyword,
give it some parentheses,

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curly brackets, and we're ready.

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Next, we need to pass in two
variables to our function.

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$form,

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&$form_state.

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Their names are defined by
the documentation of the hook,

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which you can find in the teachers notes.

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The first one, $form, is the one that
we created in the function sum_form.

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It defines which fields
the forms should display.

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But what is this one?

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After the form is submitted all
of the user supplied details or

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stored in another large
array called form state.

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This array also includes additional
information, such as the form's HTML ID.

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We're going to set the value of
the redirect key in this array

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to the string success.

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This tells Drupal where to send our form.

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So I'm going to say, $form_state.

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You don't need to use the & once
you are inside of the function.

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And give it some square brackets,
pair of quotes and

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I am setting the redirect key equal
to the value of the string success.

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Don't forget the semicolon.

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Now let's try submitting your form.

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I've already cleared my cache and
reloaded the module.

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So let's click on Calculate Sum and
fill it out.

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I'll click on the Calculate Sum
button to submit the form.

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And this time we're
redirected to a new URL,

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localhost:8888/success.

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Just as we defined in
the form_state array,

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we are redirecting to the URL success.

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For now, we're seeing page not
found when we submit the form, but

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that makes sense because we haven't told
Drupal to create the success page yet.

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Let's do that next.

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Remember, if you don't see any changes on
your site after you've changed your module

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code, then clear your cash,
disable, and re-enable your module.

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We need to add a key value pair
to the items array in hook menu,

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linking the URL's success to a page
call back function that we will write.

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So I'm going to say, items at success

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is equal to a blank array for now.

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We can fill this in with
our attributes in a moment.

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Now, let's write the page
callback function.

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We're going to call it, sum_success.

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Give it is parentheses and curly brackets.

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And this function will just print

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the message, you calculated a sum.

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We use the return keyword because
we are just returning some HTML,

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and then a semicolon.

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Now let's finish filling out
the attributes for the URL and hook menu.

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First I'll give it a title.

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Let's call it, success.

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Don't forget the comma.

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Next, we don't want a link for

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the success page the page to
appear in our navigation menu.

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The page should automatically appear
when the user submits the form.

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To hide that page from the menu,
set the type attribute to be MENU_CALLBACK

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instead of MENU_NORMAL_ITEM.

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And finally, let's not forget
to set our access callback

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to be true, so that anyone can view
the page if they submit the form.

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Next, let's actually calculate
the sum of the two form fields.

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In Drupal, when a form is submitted,
form data is passed

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to hook form submit inside
of the form state array.

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The actual form data is stored
in the values key of that array.

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We'll pull the numbers our user
entered out of this nested array, and

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do our calculation inside of the hook
form submit function, like this.

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In the first line,
we create a variable called first number.

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And will store the value from
the first form field in it.

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To get to that number,
we look inside of the form state array

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at the key values, which is also an array.

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So we look inside of that array for

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the key named after our field left_number.

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And don’t forget the semicolon.

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Here is where we defined that left_number.

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Let’s do the same for the other number,
which is here, right_number.

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And we’ll put it inside of another
variable, which we'll call.

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Second_number.

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Don't forget to change
that to right_number.

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And now,
we can add the two numbers together and

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store the solution in
a variable called sum.

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So sum = first_number + second_number;.

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But if we try this out our success page
will just say you calculated a sum.

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How do we display the sum on the new page?

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The simplest way is to store our data
as a session variable like this.

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$_SESSION is another associative array.

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It is a special variable,
built into the PHP language.

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Which can be accessed from
anywhere in your code.

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It give us a place to store information so

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that we can use it on multiple
pages in our website.

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We're calculating the answer to our
sum when the form is submitted.

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So at that time, we're still on
the page at URLLocalhost8888/sum.

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Then, we want to redirect to a new
page at URL/success to show to answer.

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So, after we process the form,
we store its data

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inside of this session so
that we can display it on a new page.

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We store our answer in the session array
by creating a key value pair in it,

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just like with any other array.

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The key is sum_output.

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And I just chose that name.

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It could be any name that
isn't already in use.

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And we're going to set it equal to
the value of our calculated sum.

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Then inside of our sum_success function,
we can get the answer to display

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by looking inside of that session
array at the key which we created,

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sum_output.

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And it will give us the value of
the sum which we can then print.

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Okay, let's try out our new module and
see if it works.

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I have already cleared the cache.

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I have disabled and
re-enabled the module just to be safe.

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And I've logged out of the site just so

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that we can see what this looks
like to a normal, anonymous user.

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So I will click on calculate sum,

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enter in two numbers to add,
and click on the submit button.

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Oh, no!

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Access denied?

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Something is up here.

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Let's go take a look at our code and
see what's going on.

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Well, first of all,
I check the access callback.

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It's set to true, so really, anyone
should be able to view the success page.

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But, we did forget one
important attribute here.

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We have actually not named
the page callback, so

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Drupal doesn't really know what
to do when it gets to this URL.

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We have to actually tell it to
run our function, sum_success,

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which I will put here in quotes,
comma, save.

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Let's go back in.

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And we'll have to log in and
clear our cache again.

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Once again we go to configuration,
performance,

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clear all caches and
then back to the modules page.

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And just to be safe, disable, save,
and then re-enable the sum module.

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Now let's log out and
go back to our home page and try it again.

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Calculate Sum.

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Lets add 5 and 6, calculate sum.

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Yay, you calculated a sum.

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The answer is 11.

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Congrats, you have now created your
first Drupal site from scratch.

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You've added custom content to it,
and stylized the layout.

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You've even written a couple of your own
modules and used a custom form to gather

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information from a user, process it,
then display a result on a new page.

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Cameron will be thrilled.

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But remember, we've only just scratched
the surface of what Drupal has to offer.

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Keep digging and exploring.

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Drupal is completely open source and
has a very friendly and helpful community.

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See the teachers notes to find more
resources to find more resources

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for where to go next.

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Bye for now.