PHP Tutorial: A Simple PHP Program, Arithmetic Operators (Page 5)

Internet & World Wide Web How to Program, 3/e
	ISBN: 0-13-145091-3 © 2004 pages: 1420 Order

This tutorial presents four PHP programs that introduce PHP programming concepts, including comments, variables, operators, keywords, type conversions, scripting delimiters, interpolation, string concatenation, control statements and arrays. The techniques you learn hear are used in our subsequent tutorials:

String Processing and
Regular Expressions
Form Processing and Business Logic

Download the code examples for this tutorial

[Note: This tutorial is an excerpt (Section 26.2) of Chapter 26, PHP, from our textbook Internet & World Wide Web How to Program, 3/e. This tutorial may refer to other chapters or sections of the book that are not included here. Permission Information: Deitel, Harvey M. and Paul J., INTERNET & WORLD WIDE WEB HOW TO PROGRAM, 3/E, ©2004, pp.900-909. Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.]

26.2 Introduction to PHP Programming (Continued)

Arithmetic Operators

PHP provides a variety of arithmetic operators, which we demonstrate in Fig. 26.4. Line 14 declares variable $a and assigns it the value 5. Line 18 calls function define to create a named constant. A constant is a value that cannot be modified once it is declared. Function define takes two arguments-the name and value of the constant. An optional third argument accepts a boolean value that specifies whether the constant is case insensitive-constants are case sensitive by default.

Common Programming Error 26.4

Assigning a value to a constant after a constant is declared is a syntax error.

Fig. 26.4 Using PHP's arithmetic operators. (Part 1 of 3.)

1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

4

5

7 <html xmlns = "http://www.w3.org/1999/xhtml">

8 <head>

9 <title>Using arithmetic operators</title>

10 </head>

12 <body>

13 <?php

14 $a = 5;

15 print( "The value of variable a is $a " );

17 // define constant VALUE

18 define( "VALUE", 5 );

20 // add constant VALUE to variable $a

21 $a = $a + VALUE;

22 print( "Variable a after adding constant VALUE

23 is $a " );

25 // multiply variable $a by 2

26 $a *= 2;

27 print( "Multiplying variable a by 2 yields $a " );

29 // test if variable $a is less than 50

30 if ( $a < 50 )

31 print( "Variable a is less than 50 " );

33 // add 40 to variable $a

34 $a += 40;

35 print( "Variable a after adding 40 is $a " );

37 // test if variable $a is 50 or less

38 if ( $a < 51 )

39 print( "Variable a is still 50 or less " );

41 // test if variable $a is between 50 and 100, inclusive

42 elseif ( $a < 101 )

43 print( "Variable a is now between 50 and 100,

44 inclusive " );

45 else

46 print( "Variable a is now greater than 100

47 " );

49 // print an uninitialized variable

50 print( "Using a variable before initializing:

51 $nothing " );

53 // add constant VALUE to an uninitialized variable

54 $test = $num + VALUE;

55 print( "An uninitialized variable plus constant

56 VALUE yields $test " );

58 // add a string to an integer

59 $str = "3 dollars";

60 $a += $str;

61 print( "Adding a string to variable a yields $a

62 " );

63 ?>

64 </body>

65 </html>

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Other PHP Tutorials
PHP Tutorial 1: Introduction to PHP
PHP Tutorial 2: Creating Simple PHP Programs (You are here)
PHP Tutorial 3: String Processing and Regular Expressions
PHP Tutorial 4: Form Processing and Business Logic