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Let's take what we've learned about variables and operators to create a simple unit converter that can convert pounds to kilograms and miles to kilometers.
Conversions
$lb_to_kg = 0.453592;
$mile_to_km = 1.60934;
1 pound = 0.453592 kilogram
1 kilogram = 2.20462 pounds
1 mile = 1.60934 kilometers
1 kilometer = 0.621371 miles
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Let's take what we've learned about
variables and operators to create a simple
0:00
unit converter that can convert pounds
to kilograms and miles to kilometers.
0:04
You can reverse these calculations,
0:09
as well, to determine the number of miles
in a kilometer, and pounds in a kilogram.
0:10
Check the teacher's notes for
0:15
more of the equations used to
calculate these conversions.
0:17
Do you remember the two
basic parts of writing code?
0:20
The storage and retrieval of data and
the logic that tells what and
0:23
when to do something with that data.
0:27
So first we'll need to store two pieces
of data, the floating point value for
0:30
the conversion and
the number we want to convert.
0:34
Then we'll retrieve that data and
perform the calculations.
0:38
Then we'll finally display the results.
0:41
So let's get started.
0:44
Let's create a new file named units.php.
0:46
We start by adding the opening and
closing php tags and
0:53
then we're ready to start
writing our program.
0:56
Comments are a great way to start.
1:00
So let's outline what we'll
be doing using comments.
1:02
Let's start with pounds to kilograms.
1:05
The first thing we need
is number in pounds
1:08
that we want to convert to kilograms.
1:14
Then we need the floating point value for
1:21
the pound to kilogram conversion.
1:27
Then we'll use the variables
1:34
above to calculate pounds multiplied
1:40
by the kilogram conversion.
1:46
And finally,
we display the pounds to kilograms.
1:53
Then we'll also convert
miles to kilometers.
2:00
Again, we start with
the number in miles we want to
2:04
convert to kilometers.
2:10
Then we need the floating point value, For
2:17
the mile to kilometer conversion.
2:22
Then we need to use the variables
2:29
above to calculate miles multiplied
2:34
by the kilometer conversion.
2:41
And finally,
we'll display the miles to kilometers.
2:46
Now we're ready to start
creating our variables.
2:53
We'll start with our
variable name $pounds.
2:58
You can assign this
whatever value you want.
3:01
I'm going to use 140.
3:04
We'll then create our next
variable named $lbs_to_kg.
3:07
And we'll set this equal to 0.453592,
3:14
which is how many kilograms
go into one pound.
3:18
We can now perform the calculation and
3:24
assign it to a third
variable named $kilograms.
3:26
$pounds * $lb_to_kg
3:32
will give us our kilograms.
3:37
And finally,
we can display the results to the screen.
3:43
Let's start this with some text.
3:49
Our weight, Echo our $pounds.
3:51
Then we'll echo some more text.
4:00
Our lb = $kilograms.
4:03
Echo "kg".
4:10
Now, let's run the script and
see what we get.
4:15
Great, just what we want.
4:19
The weight, 140 pounds,
4:22
equals 63.50288 kilograms.
4:25
Let's add a space right here.
4:30
And now we're ready to set
up our miles to kilometers.
4:33
We start with a variable named $miles and
we'll set this equal to 2.5.
4:39
We then create a variable
named $mile_to_km and
4:46
we'll give it a value of 1.60934,
4:51
which is how many
kilometers are in one mile.
4:54
Now we perform the calculation and assign
it to the third variable, $kilometers.
5:01
$miles * $mile_to_km will
give us our kilometers.
5:09
And finally,
we display the results to the screen.
5:18
Echo our text will say "Distance:".
5:23
Echo our $miles and
5:28
then "miles =",
5:33
our $kilometer.
5:37
And then we'll echo out km.
5:44
Now let's run the script and
see what we get.
5:50
Great, we can see distance
added to the end.
5:54
2.5 miles equals 4.02335 kilometers.
5:58
We'll learn more about
formatting in the next section.
6:04
Fantastic job putting your new knowledge
of variables and operators to work.
6:08
Can you reverse the operations and
convert kilograms to pounds, and
6:13
kilometers to miles?
6:16
Or choose a different conversion to
implement, such as Fahrenheit to Celsius?
6:18
As you practice,
6:23
you'll become much more comfortable with
using your PHP skills to solve problems.
6:23
In the next section,
we'll explore different data types for
6:29
variables, use conditional operators, and
6:32
start implementing conditional logic
to create a daily exercise program.
6:35
So hurry back to continue
flexing our muscles.
6:40
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