WEBVTT

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The next loop we'll look at is a for loop.

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For loops are the most
complex loops in PHP,

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because they use three
expressions instead of just one.

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[SOUND] The first expression
is executed once,

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unconditionally at
the beginning of the loop.

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At the beginning of each iteration
expression two is evaluated.

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This is the conditional part if it
evaluates to true the loop continues and

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the statement block is executed.

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If it evaluates to false
the execution of the loop ends.

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At the end of each iteration
expression three is executed.

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We actually used all these
pieces in our while loop but

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now we can put them together in one place.

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Complex doesn't need to mean difficult.

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Sometimes having something
more complex in one place

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is actually easier to read than
looking for all the simple pieces.

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Let's take a look at how we can write
our list of years using a for loop.

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Let's go back to the loops.php file,
and comment out the while loop for

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our learn array.

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Then let's go back up to the top
of our file, and add our for loop,

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right below our variables.

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We start with the keyword for, and

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then our parentheses followed
by the curly braces.

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Now we can add the expressions, The first
expression gives us our starting value.

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So we'll move the year into our for loop.

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The second expression is the conditional,
so we copy that from our while loop.

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The third expression is for telling the
loop how to update values after each loop.

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We already have the iterator as
part of the conditional, and a for

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loop will allow us to leave off
any of the three expressions.

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This means that the for
loop is perfectly valid now.

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So I'm gonna leave it like
this just to demonstrate.

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Now we can copy the statement
block from our while loop as well.

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And we're ready to test
this out in the browser.

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We see the years 1917 through 2016 again,

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because we're iterating
before displaying the year.

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Let's move the iteration to
the third expression of our loop.

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Instead of the ++ being
here, we'll add year++.

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Now when we refresh our browser,
we see 1916 through 2016 because

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the final expression is not executed
until the end of the for loop.

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Let's clean this up a little more.

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I could move the current year into the for
loop,

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by separating these first two
expressions with a comma.

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That means both these expressions
will run before our first loop.

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Let's refresh the browser,
and our page still works.

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Now instead of the current year I
could just use the date function.

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And instead of subtracting 100,
I'll just subtract 99.

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Now when we refresh the browser
we see 1917 through 2016.

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You'll often see for loops used when
looping through numbers such as these.

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You can also use a for
loop with indexed arrays

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as long as the keys are sequential and
no keys have been skipped.

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This will work well on my learn array
if I use the sort to re-index the keys,

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let's take a look.

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We'll comment this out, and
then we'll move down here.

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Instead of asort, I want to just use sort,

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then we'll set up the structure for
our for loop, for () { }.

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Then we can start adding our expressions.

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First we start with our initial variable.

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This is going to be an integer, so
we can name int or just i for short.

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Then we can set i = 0 since
our keys are zero indexed.

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Then we can add our conditional.

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We want to loop while i

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is less than the number of
items in the learn array.

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So we'll use another handy little function
named count, which does just that.

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It counts the number of
items in a given array.

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So we'll pass at the learn array.

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Then we add our final expression
to iterate through i.

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Now we're ready to display
each of those items.

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We start with echo $learn and
then within square brackets we use i.

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This holds the key value
that we want to use.

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Finally let's concatenate a line break.

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Now let's run the script in the console.

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We see our list of to do
items sorted by value again.

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Great job.