Assignment034

PHP Index

In order to become familiar with PHP programming structures and commands, we will build various PHP pages. Sections of this page will explain each PHP command, provide a link to a working sample, and detail the working sample's PHP code. Let's get started:

Constants

Now that you have been introduced to variables, it is time to learn about 'fixed' variables, or constants. Constants are variables that are assigned a semi-permanent or permanent value. For example, you might want to define a constant variable to hold sales tax percentage. Sales taxes tend to stay the same over an extended period of time, however, sales taxes might go up (or down). A constant allows you to define your fixed variable in one place. If there is a change, you only need to update your constant definition and your code will continue to work.

Define constants using the define function, like so:

define("SALES_TAX", .07859358);

define("TEACHER", "Mr. Chagoyan");

define("PI", 3.1415926535);

It is good practice to use all capitals for your constant names for easy identification.

Here's another example: constants.php

 <html>

  <head>

  <title>constants.php</title>

  </head>

  <body>

            <?php

            //Interest Calculation

            

            //Set the variables and constants

            define("INTEREST_RATE", .19);

            $balance1=115000.00;

            $balance2=15000.00;

            $balance3=177000.00;

            $balance4=10000.00;

            

            //Calculate the annual interest amounts for each balance

            $annualinterestamount1 = $balance1*INTEREST_RATE;

            $annualinterestamount2 = $balance2*INTEREST_RATE;

            $annualinterestamount3 = $balance3*INTEREST_RATE;

            $annualinterestamount4 = $balance4*INTEREST_RATE;

            

            //Display browser output

            print("The annual interest due on your first balance of ".$balance1); 

            print(" is ". $annualinterestamount1). " dollars.";

            print("<br><br>");

            

            print("The annual interest due on your second balance of ".$balance2); 

            print(" is ". $annualinterestamount2). " dollars."; 

            print("<br><br>");

            

            print("The annual interest due on your third balance1 of ".$balance3); 

            print(" is ". $annualinterestamount3). " dollars."; 

            print("<br><br>");

            

            print("The annual interest due on your fourth balance of ".$balance4); 

            print(" is ". $annualinterestamount4). " dollars."; 

            print("<br><br>");

            

   

            ?>

            

  </body>

  </html>