OOP with PHP

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OOP with PHP

• Roman Bednarik
• rbednari_at_cs.joensuu.fi

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OOP with PHPlecture outline

• What is PHP
• Why use OOP with PHP
• OOP with PHP
• Advanced topics on OOP and PHP

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OOP with PHPwhat is PHP? - development

• PHP PHP Hypertext Preprocessor
• Originally a collection of scripts
• Developed as open source
• Major revision in 2001
• In 2001 5 millions of domains using PHP
• In Oct 2002 9 millions !
• Nowadays in version PHP4 (PHP 4.3RC2) this
  lecture
• PHP5 in development

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OOP with PHPwhat is PHP? - usage

• Server side scripting generating (not only) HTML
• Strong association with the Apache server and
  MySQL
• Many OS covered
• Great number of additional modules

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OOP with PHPwhat is PHP? - characteristics

• Interpreted
• Loosely type checking
• Overloading not supported
• Enables references
• Case sensitive
• Variable variable names
• Associative arrays
• Serialization of objects into the stream

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OOP with PHPwhat is PHP? - example
PHP source (example.php) lthtmlgt ltbodygt lt?php A
1 B 2 C A B echo Result of
AB.C echo ltBRgt\n echo Hello
world! ?gt lt/bodygt lt/htmlgt
Browser view Result of 12 3 Hello world!
HTML output lthtmlgt ltbodygt Result of 12
3ltBRgt Hello world! lt/bodygt lt/htmlgt
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OOP with PHPlecture outline

• What is PHP
• Why use OOP with PHP
• OOP with PHP
• Advanced topics on OOP and PHP

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OOP with PHPwhy OOP in PHP

• Common OOP approach advantages
• Modularity
• Less code
• Reusability
• Robustness
• Handling large projects, easy to maintain
• Classes usually reflect database schema
• PHP is not inherently OOP language!

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OOP with PHPwhy OOP in PHP examples

• Online shops
• Banking systems
• News services
• Editors' systems
• Home pages
• gt use OOP to separate the functionality from
  layout

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OOP with PHPlecture outline

• What is PHP
• Why use OOP with PHP
• OOP with PHP (or PHP with OOP?)
• Advanced topics on OOP and PHP

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OOP with PHPcharacteristics

• PHP fulfills
• Abstract data types
• Information hiding
• Inheritance
• Polymorphism
• PHP fails
• Later on ..
• Almost all can be resolved by some of the
  'workarounds'

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OOP with PHPcase class

• lt?php
• class FirstClass
• var x // data member no ways of specifying
  private/protected
• function setX (a)
• this-gtx a
• function getX ()
• return this-gtx
• function printX() echo this-gtx
• // class
• instanceA new FirstClass

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OOP with PHPAbstract data types

• Both we have in PHP classes
• Data integer, string, array, associative array,
  object
• In PHP no data protection, public is default
• Methods defined as a member functions
• e.g function setData1 (aData1default)
• this -gt Data1 aData1

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OOP with PHPInformation hiding encapsulation

• Good practice is to use set and get methods to
  access the member structures
• C, Java, Ada etc. allow protected/private/public
  
• PHP only public by default

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OOP with PHPInheritance

• In PHP using keyword extends
• lt?php
• class SecondClass extends FirstClass
• var Y
• function setY (a)
• if ( getX()gt0) this-gtY a // getX
  inherited
• else this-gtY 0
• ?gt
• Multiple inheritance is not supported

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OOP with PHPPolymorphism

• All class member functions are virtual by the
  definition
• class A
• function draw() echo "1" // not
  needed
• function boo() this-gtdraw()
• class B extends A
• function draw() echo "drawing B"
• b new B()
• b-gtboo() // outputs drawing B

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OOP with PHPconstructors

• All initialization has to be done in constructor
• No constructor chaining! gt when an object as an
  instance of derived class is created, only it's
  constructor is called. If does not exist,
  parental constructor is called.
• Solution
• Explicit constructor call
• parent name_of_parent_class()
• No destructors in PHP automatic garbage
  collection

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OOP with PHPabstract classes

• Abstract class is not instantiable
• No standard way in PHP
• Solution
• Call die in the constructor and methods
• if the method is not overridden in a derived
  class the error occurs

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OOP with PHPstatic variables

• One instance for all objects of the class
• No standard way in PHP
• Workarounds
• Global variables giving a reference of global
  variable in each constructor call (creation)
• e.g.

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OOP with PHPstatic variables

• GLOBALS'_transient''static''test'-gtv1 1
  // global storage
• class Test
• function Test() // constructor
• this-gtv1 GLOBALS'_transient''stat
  ic''test'-gtv1 // link a new variable
• function printAndIncrease()
• echo "this-gtv1 ltbrgt"
• this-gtv1
• var v1
• test1 new Test() // invokes constructor
• test1-gtprintAndIncrease()
• test2 new Test()
• test2-gtprintAndIncrease()

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OOP with PHPPHP fails on

• No templates
• No private/protected members
• No casting from one class to another
• No static class variables
• No interfaces
• No exceptions
• gt many to be resolved in PHP5

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OOP with PHP

• lt?php
• class Element //basic class for all elements
  
• function Element(caption"")
• this-gtSetup(caption)
• function Setup(caption)
• this-gtcaption caption
• function Set() //virtual methods
• function Get()
• function GetCaption()
• return this-gtcaption
• function Print_()
• ?gt

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OOP with PHP

• lt?php
• include_once("class.element.php")
• class Button extends Element //inheritance
• function Button(caption"",action"")
• this-gtSetup(caption,action)
• function Setup(caption,action)
• this-gtcaption caption
• this-gtaction action
• function Print_()
• echo "ltINPUT TYPEbutton "
• if (this-gtcaption) echo "VALUE\"this-gtcaptio
  n\" "
• if (this-gtaction) echo "OnClick\"this-gtactio
  n\" "
• echo "gt\n"
• ?gt

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OOP with PHP

• lt?php
• include_once("class.element.php")
  include_once("class.button.php")
• class Page
• var reload
• function Page(caption"",obj)
• this-gtSetup(caption,obj)
• //add the properties and elements common to
  all pages
• this-gtreload new Button("Reload","document.loca
  tion.reload()")
• function Setup(caption, obj)
• this-gtcaption caption
• this-gtobj obj
• function GetCaptions()
• for (i0 ilt count(this-gtobj) i)
• echo this-gtobji-gtGetCaption() echo
  "ltBRgt"

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OOP with PHP

• function print_()
• echo "ltHTMLgt\n ltHEADgt\n ltTITLEgt"
• if (this-gtcaption) echo "this-gtcaption"
• echo " lt/TITLEgt\n"
• echo " lt/HEADgt\n"
• echo " ltBODYgt\n"
• this-gtreload-gtPrint_()
• for (i0 ilt count(this-gtobj) i)
  //invoke Print_() for all
• //elements on page
• this-gtobji-gtPrint_()
• echo "ltBRgt"
• echo " lt/BODYgt\n"
• echo "lt/HTMLgt\n"
• ?gt

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OOP with PHPhttp//cs.joensuu.fi/pages/bednarik/O
OP/example.php

• lt?php
• include("class.element.php")include("class.button
  .php")
• include("class.table.php")include("class.page.php
  ")
• tab new Table()
• tab-gtSetup("My table 10x3",10,3)
• tab2 tab
• tab2-gtSetup("My table 2 3x3",3,3)
• but new Button("Click me","alert('Hello')")
• obs0 tab
• obs1 tab2
• obs2 but
• page new Page("Object Page",obs)
• page-gtPrint_()
• page-gtGetCaptions()
• ?gt

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OOP with PHPlecture outline

• What is PHP
• Why use OOP with PHP
• OOP with PHP
• Advanced topics on OOP and PHP

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OOP with PHP

• Generic function for setting the member variables
• function Set (varname, value)
• this-gtvarname value
• instance-gtSet ('size','5')

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OOP with PHPSerializing the objects

• Partially overcomes the need for a persistent
  object
• !!Saves only data members, not methods! (PHP4 is
  exception)
• lt?php
• myCart new ShoppingCart()
• stream1 serialize(myCart) // and store to
  file or db
• ...
• ... // retreive from file/db after a year..
• myLaterCart unserialize(stream1)
• ?gt
• Not recommended to use!

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OOP with PHPOverloading in PHP

• lt?php
• class ShoppingCart
• function ShoppingCart()
• to_call"ShoppingCart".func_num_args()
• args func_get_args() // return an array of
  arguments
• args implode('',args)
• args str_replace(, ,, args)
• run \this-gtto_call (args) //
  variable variable
• eval (run)
• function ShoppingCart1(x2) code1()
• function ShoppingCart2(x2,y3) code2()
• ?gt

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OOP with PHPSerializing the objects (cont.)

• Stream is a string with defined format
• One might try to investigate it
• myCart new ShoppingCart()
• stream1 serialize(myCart)
• hocus explode('',stream1) // split stream1
  by into array
• e.g.
• classname str_replace( \, '' ,hocus2 )
  // takes away the

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• USE OOP!
• Thank you