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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

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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