Internet%20Services

1
Internet Services

• PHP
• Introduction

2
Objectives

• By the end of this lecture the student should
• Understand the advantages and disadvantages of
  server-side scripting
• Understand the basic structure of PHP
• Understand that it is the programmers
  responsibility to ensure correct HTML and correct
  use of variables

3
PHP Recommended Books

• Teach Yourself PHP in 24 Hours
• Matt Zandstra
• Essential PHP fast
• Simon Stobart

4
PHP

• Personal Home Page
• Server-side scripting
• Server interprets and sends HTML document to
  browser
• Available at
• www.php.net
• Server from
• www.omnicron.ca
• (doesnt need PHP)

5
Server-Side Scripting

• Advantages
• Browser independent
• Run programmes not supported by browser
• Access data not on browser
• Security

6
Server-Side Scripting

• Disadvantages
• Requires access to server to process input
• Validation more difficult than with, say,
  JavaScript

7
PHP

• Embedded within HTML
• lt?php ?gt tags
• Similar to C, Perl

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Example Code

• lthtmlgt
• ltheadgt
• lt/headgt
• ltbodygt
• lt?php
• echo(Hello ltbgtWorld!lt/bgt)
• ?gt
• lt/bodygt
• lt/htmlgt

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Look at the Source Produced

• lthtmlgt
• ltheadgt
• lt/headgt
• ltbodygt
• Hello ltbgtWorld!lt/bgt
• lt/bodygt
• lt/htmlgt

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Example Output

• Hello World!

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Programmers Responsibility

• Programmers responsibility to ensure html is
  correct
• echo(Hello ltwgtWorldlt/bgt) will produce?
• Hello World
• Hello World
• Hello ltwgtWorldlt/bgt
• Hello ltwgtWorld

12
PHP

• Comments
• // or for single lines
• / / spans multiple lines

13
Variables

• PHP supports
• Integers
• Floating point (double)
• Strings
• Boolean
• Arrays
• Objects
• Start with followed by _ or letter
• Is not strongly typed

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Variables

• May be assigned by
• Value
• var1var2
• var1123
• Reference
• var1var2
• Output with echo statement
• echo(Value is . var1 . units)
• . Concatenates a string

15
Variables

• Print may also be used
• gettype() checks type
• settype(var,type) changes type
• var1( type ) var2 also changes type
• But
• var12
• var2hello
• var2var2 . var1
• is OK, as is
• var2var2var1

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Variables

• lt?php
• var1123
• echo("var1 was . var1 . "ltbrgt")
• var112.3
• echo("var1 is now . var1 . "ltbrgt")
• var1"Hello Fred"
• echo("and now it is . var1."ltbrgt")
• ?gt
• var1var12 is also allowed here so beware!

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Summary

• PHP is server-side scripting
• Script is interpreted by the server, which sends
  HTML to the browser
• Programmers responsibility to ensure HTML is
  correct
• Normal range of types allowed
• But PHP is not strongly typed
• Programmers responsibility to use variables
  correctly