Dr. Natalio Krasnogor

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G64HLL High-Level Languages Lecture 5

• Dr. Natalio Krasnogor
• Natalio.Krasnogor_at_Nottingham.ac.uk

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What were going to look at

• This is the shortest and easiest section of HLL
• Were going to look at
• What the heck PHP is
• Why PHP is so bloody great
• Why its (in some cases) preferable to
  JSP/ASP..(even perl)
• How to code properly in PHP
• How to use PHP to create web applications/database
  s..

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Short Learning Curve

• For a long time, the primary language used to
  develop such Web sites was Perl.
• Ask any novice programmer, and he'll tell you
  that learning Perl isn't exactly a bed of
  roses...
• There has been a proliferation of alternative
  server-side scripting languages that have a
  shorter learning curve.
• PHP has the unique distinction of being an
  open-source server-side scripting language that's
  both simple, powerful and easy to learn.

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Recommended Reading

• PHP and MySQL Web
• Development
• (1st or 2nd edition)
•  
• Luke Welling,
• Laura Thomson
• 25.55 (Amazon.co.uk)

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References Web

• http//www.firepages.com.au/phpdev4.htm
• A great php server (install it)
• http//www.php.net
• The best Php site
• http//www.phpfreaks.com
• http//www.phpbuilder.com

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A choice of editing programs

• Windows - JFE
• UNIX - Nedit
• Make sure you check
• The sh-bang ! on the university systems
• The sh-bang is not there if its not needed
• The security on the php file (chmod 755 )
• That you have the php in the correct folder

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1. PHP HISTORY

• PHP is a language for creating interactive web
  sites. It was originally called "Personal Home
  Page Tools" when it was created in 1994 by
  Rasmus Lerdorf to keep track of who was looking
  at his online CV.
• Mid-1997 Technion (Israel) students Andi Gutmans
  and Zeev Suraski redesigned the PHP language
  engine and wrote some of the most popular PHP
  modules.
• At that time PHP already had its own site,
  php.net, run by the computer science community,
  and was powering thousands of Web sites.

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Recursive Names

• PHP originally stood for
• Personal Home Pages.
• PHP is now a recursive acronym that stands for
• PHP Hypertext Preprocessor

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These Dates are recent

• Version 0.0 Conceived in autumn of 1994
• Version 1.0 Personal Home Page Tools in early
  1995
• Version 2.0 PHP/FI 1995-1997
• Version 3.0 PHP 1997-2000
• Version 4.0 PHP mid-2000
• Version 4.1 10 Dec 2001
• Version 4.2 22 Apr 2002
• Development Team (515 people with CVS commit
  access).
• Today PHP Web developers applaud the script's
  simplicity, flexibility, and ability to generate
  HTML pages quickly.
• At start of 2001 gt 5,100,000 sites around the
  world used PHP.

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PHP Usage May 2002
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Hello World!

• Hello World in Pascal
• program hello
• begin
• writeln('Hello World')
• end.

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Hello World!

• Hello World in Java
• class hello
• public static void main(int args, char argv)
• System.out.println("Hello World")

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Hello World!

• Hello World in Perl
• print "Hello World"

• Hello World in PHP
• Hello World

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2. PHP Style

• PHP Style Programming
• ltHTMLgt
• ltHEADgt
• ltTITLEgtSearch results for "lt?php print
  query?gt"lt/TITLEgt
• lt/HEADgt
• ltBODYgt
• Traditional Perl Programming
• !/usr/bin/perl
• print "ltHTMLgtltHEADgt\n"
• print "ltTITLEgtSearch results for
  \"query\"lt/TITLEgt\n"
• print "lt/HEADgt\n"
• print "ltBODYgt\n"

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An Embedded Script?

• You could view PHP as an embedded language.
• Unlike perl which can print HTML out PHP does
  this by default.
• However it is very much still a Server Side
  Language this is not the same sort of thing as
  Javascript

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PHP Tag Styles The bad

• Script Style
• ltSCRIPT LANGUAGEphpgt
• print this is script style
• lt/SCRIPTgt
• ASP Style
• lt
• print this is ASP style
• gt
• Both these styles of opening code is perfectly
  valid but they are based on other languages.

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PHP Tag Styles The good

• XML Style
• lt?php
• print this is XML style
• ?gt
• Short Style
• lt?
• print this is ASP style
• ?gt
• To use Short style the PHP you are using must
  have short tags enabled in its config file
  this is almost always the case.

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Switching Modes

• lt?
• if(strstr(HTTP_USER_AGENT,"MSIE"))
• ?gt
• ltbgtYou are using Internet Explorerlt/bgt
• lt?
• else
• ?gtltbgtYou are not using Internet Explorerlt/bgt
• lt?
• ?gt

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PHP is C Style

• PHP, just as perl is, is very similar to C.
• This is because C is top banana.
• As a consequence if you know java (also a c
  clone), C or indeed almost any other computer
  science language you pretty much already know
  PHP.
• However more than anything PHP is based on Perl.

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Creating a PHP program

• You can use any text editor
• Different server setups work in different ways
• University start with the good old sh-bang
• Most other systems on the web know that if your
  file has a .php extension you are using PHP.
• Use lt? To open your code and ?gt to close it.
• Anything not in those tags is rendered as HTML.
• Type your code and load it up in a web browser.

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Running your PHP program

• The ! Line for PHP on the CS machines is
• !/usr/bin/php
• You'll also need to tell UNIX that your file is
  executable, by typing an appropriate chmod line
  into the UNIX shell
• chmod 755 hello.php
• If just typing the filename doesn't run the
  program, try
• ./filename

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Comments

• Why do we go on about comments so much?
• because without them, marking would hurt our
  heads is GOOD PROGRAMMING PRACTICE.
• lt? //C style comment
• perl style comment / C
  multi line comment /
• ?gt

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God, please, no more Hello World programs

• Hello World now looks like
• !/usr/bin/php
• ltHTMLgt
• Hello World
• lt?
• print Is it meeeee your looking foooor\n"
• // Hello World - By Jim and Lionel Ritchie
• ?gt
• lt/HTMLgt

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4. PHP is for Lazy People

• Yup, you know that means you!
• Basic data types
• numbers (integers and real)
• strings (Double-quoted "abc and single-quoted
  'abc' )
• booleans (true,false )
• Dynamic typing
• Don't have to declare types
• Automatic conversion done

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Variables in action

• lt? x  false         // boolean x  true
  x  10         // decimal x  1.45        
  // Floating point x  0x1A         // hexade
  cimal  x  "mmm\"oo'oo\n"     //  mmm"oo'oo  a
  nd a new line x  'mmm"oo'oo\n'     // string 
   mmm"oo'oo\n y  x         // Reference
  x1  10         // array of decimals
  x"name"  jimbo"    // associative array
  x2"lala"  "xx"    // a two dimensional
  array
• ?gt

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Printing out Variables

• lt?
• name  Winnie the Pooh" friends  array(don
  key" gt Ee-or" , tiger" gt tigger")
• print friendsdonkey
•   print hid all of
• print name s weapons of mass destruction
• ?gt
• OUTPUT
• Ee-or hid all of Winnie the Pooh s Weapons of
  mass destruction

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Type conversion

• Conversion between types can be pure or dirty
• forced casting
• lt? 
• bool  true print (int)bool 
• ?gt
• Type Juggling
• lt? x  "100" x
  // x is now 101 ?gt

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Variable Scope

• The 3 basic types of scope in PHP are
• Global variables declared in a script are visible
  throughout that script, but not inside functions
• Variables used inside functions are local to the
  function
• Variables used inside functions that are declared
  as global refer to the global variable of the
  same name

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Numerical functions as per normal

• Addition
• a 1 1 // sets a to 2
• a 4 // adds 4 to a
• a // adds 1 to a
• Subtraction
• a 10 - 5 sets a to 5
• a - 6 subtracts 6 from a
• a-- subtracts 1 from a

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Final Numerical functions

• Multiplication
• a 2 3 // sets a to 6
• a 10 // multiplies a by 10
• Division
• a 10 / 3 // sets a to 3.3333
• a / 2 // halves a
• Modulus
• a 10 3 // sets a to 1
• a 2 // sets a to modulus 2
• // of itself

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PHP Operators

• Addition - Subtraction
  Multiplication / Division Modulus
  And Or Xor . add string (like in
  perl) ltlt Shift left gtgt Shift right

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Simple String functions

• chr - Return a specific character
• ord - Return ASCII value of character
• sprintf - Return a formatted string
• strlen - Get string length
• strpos - Find position of first occurrence of a
  string
• strrev - Reverse a string
• strtolower - Make a string lowercase
• strtoupper - Make a string uppercase
• str_replace - Replace all occurrences of the
  search string with the replacement string

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Deja Vu

• Just for the record whats the same as C/Java?
• For Loops
• While Loops
• If Statements
• Break, Continue, Exit, Switch, etc.
• The main concepts which differ in syntax are
• Functions
• Classes

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More déjà vu If statements

• if statements
• if (some test)
• // code here
• else if (some other test)
• // code here
• else
• // if neither test met, do this

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Conditional tests

• Equals
• gt Greater than
• lt Less than
• gt Greater or equal to
• lt Less or equal to
• ! Not equal
• This, unlike perl, works exactly the same way for
  strings as it does for integers and floats.

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If exists

• You often need to check whether a variable exists
  in PHP.
• There are two ways to do this

if (a) print \a exists"
if (!empty(a)) print \a exists"
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Foreach loops Useful things

• lt? //valuesa  array (1, 2, 3, 17)
  foreach (a as v) 
•    print "Current value of \v v.ltbrgt"
  // values and keys a  array (1, 2, 3, 17)
  foreach(a as k gt v) 
•     print "\ak is vltbrgt"
• ?gt

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Mixing up types in Arrays

• lt?
• arr array(1,'foo',1.57,'cat'gt'mouse','dog'gt'
  mailman')
• ?gt
• lt? foreach( arr as kgtv )
•     print "\arrk vltbrgt\n"
• ?gt

Setting up an array
OUTPUT arr0 1arr1 fooarr2
1.5arrcat mousearrdog mailman
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PHP Functions

• Functions in PHP are not case sensitive.
• Be careful of this because variable naming is
  case sensitive
• function my_function()
• print My function was called
• Functions can be created anywhere in your PHP
  code
• However good style demands they should always be
  at the top of your code

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Do what is neatest

• lt?
• Function my_function()
• print My function was called
• ?gt

lt? Function my_function() ?gt My function
was called lt? ?gt
IS IDENTICAL TO
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Passing Parameters

• As normal you dont have to specify the types of
  your parameters...
• Be careful of this because variable naming is
  case sensitive
• function display_table(data)
• print ltTABLEgt
• for (i0 iltsizeof(data) i)
• print ltTRgtltTDgt datai lt/TDgtlt/TRgt
• print lt/TRgt

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Defaults Passing by Reference

• As with other languages you can set defaults. PHP
  requires that you do specify the correct number
  of parameters in a call.
• Equally you dont have to pass by value an
  ampersand will mean the variable is passed by
  reference and so any changes to it are global
• function increment(value, amount1)
• value value amount

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Returning Stuff

• The keyword return stops the execution of a
  function.
• You can have as many return statements as you
  like at any point in your function the first
  one encountered in the program flow will end the
  function.
• To return a value just add it after the keyword
  again any type can be returned.
• You dont need to specify a return type in the
  function declaration

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Example

• function larger(x, y)
• if (x gt y)
• return x
• if (x lt y)
• return y
• if (x y)
• return x and y have the same value

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Object Orientation

• Much better in PHP 4 than its previous version
• However still rather simplified
• class classname
• var attribute1
• var attribute2
• function method1()
• No real data encapsulation.
• So if you DO go object then be consistent and
  dont violate the encapsulation.

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5. PHP or ASP?

• Open source
• PHP is faster
• Superior Memory Management
• Tied up with GET and POST variables are
  automatically created as global variables
• Truly Portable
• Less Coffee Breaks
• Less cursing Microsoft
• PHP is free!?!

Need ASP email management? buy ServerObject's
QMail. Need ASP file uploading? -- buy Software
Artisans SA-FileUp. Need ASP encryption? -- buy
ASPEncrypt.
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What is PHP bad at?

• Cant really think of anything
• Sometimes hard to debug because it does so much
  for you
• Thats it.

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Summary

• PHP is easy. It does most things for you.
• From now on we will be looking at why it is Good
  as opposed to simple.
• Its tricks, features and functions are excellent.

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Thats All Folks