PHP Introduction

1
PHP Introduction

• After this lecture, you should be able to
• Know the fundamental concepts of Web Scripting
  Languages in general, PHP in particular.
• Make simple scripts with PHP
• PHP Syntax
• PHP Data Types

PHP Intro
2
Processing an HTTP Request
1
Client Browser
Apache Web Server
4
2
3
PHP Module
3
Web Scripting Languages

• Languages used to create Web pages dynamically,
• e.g., by using data retrieved from a database
• CGI Scripts and Programs
• Perl Practical Extraction and Report Language
• PHP Hypertext Preprocessor
• ASP Active Server Pages
• JSP Java Server Pages
• ASP.NET Visual Basic, C
• Python

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What is PHP?

• PHP is a scripting language used mostly
• for creating web pages dynamically.
• PHP Hypertext Preprocessor. Originally called
  Personal Home Page.
• PHP is server-side scripting.
• PHP statements can be embedded within an ordinary
  HTML page with lt?php . . . ?gt tags.
• PHP is dynamically typed.
• PHP code is interpreted.

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Simple PHP Script
lt? x 2 y 3 z x y echo 2
3 z ?gt
Output 2 3 5
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Simple PHP Web Script
lthtmlgt ltheadgt lttitlegt Hello World!
lt/titlegt lt/headgt ltbodygt lt? echo Hello
World!\n ?gt lt/bodygt lt/htmlgt

• Output
• lthtmlgt
• ltheadgt
• lttitlegt
• Hello World!
• lt/titlegt
• lt/headgt
• ltbodygt
• Hello World!
• lt/bodygt
• lt/htmlgt

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PHP Syntax

• Similar to C / Java
• Semi-colon is a statement terminator.
• Variable names start with .
• Operators and expressions are similar to those
  used by C and Java with a few additions.
• Control structures
• if-else, switch, while, do-while, for,
  foreach,
• break, continue, . . .

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PHP Data types

• Scalar types
• - boolean
• - integer
• - float (double)
• - string
• Compound types
• - array
• - object
• Special types
• - resource
• - NULL

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Variables Are Not Typed
Since a variable is not typed, a value of any
type can be assigned to it.
A 1 A abc
The type of a datum can be boolean, integer,
float, string, array, object, and resources.
NULL also can be assigned.
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Polymorphism Automatic Data Type Conversion
A 1 B 2 C A B D A .
B echo "C\n" echo "D\n" echo
C\n
Output 3 12 C\n
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Boolean Values

• echo true
• echo false
• echo 1
• echo 0
• echo true ? A B
• echo 1 ? A B
• echo 100 ? A B
• echo xx ? A B
• echo false ? A B
• echo 0 ? A B
• echo ? A B

1 (empty) 1 0 A A A A B B B
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Idiosyncrasies

• echo dog 0
• echo 0 0
• echo 0 false
• echo 0 0
• echo 0 false
• echo 100 100
• echo 100 100
• echo (int) 100
• echo (int) 100xxx
• echo (int) xxx100

1 1 1 1 (empty) 1 (empty) 100 100 0
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Evaluating a Variable within Text Mode
Evaluation lt? x 100 echo \x1 .
x echo \x2 x\n ?gt x3 lt? x ?gt
Evaluation x1 100 x2 100 x3 100
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Special Characters within

• The following special characters can be used
  within a string quoted by
• \ -- double quote
• \n -- newline
• \r -- carriage return
• \t -- tab
• \\ -- backslash
• \ -- dollar sign
• \, \), \, \

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Parameter Passing to a Function
function add(x, y) x y
return x y
a 10 b 20 echo add(a, b) . \n echo
a . \n echo b . \n
32 10 21
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Including a File

• An external file can be loaded with one of the
  following statements
• lt? include file path ?gt
• The execution continues even when the file
  to be
• loaded does not exist.
• lt? require file path ?gt
• The execution terminates when the file to
  be
• loaded does not exist.
• lt? include_once file path ?gt and
• lt? require_once file path ?gt
• A file is included only once even if it is
  requested
• multiple times.

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PHP Resources

• PHP Website - http//www.php.net
• PHP Manual Getting Started http//www.php.net/m
  anual/en/getting-started.php
• Hugh E. Williams and David Lane. Web Database
  Applications with PHP MySQL. O'Reilly, ISBN
  0-596-00041-3 (optional)
• Other resources on the web