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OOP with PHP

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Title: OOP with PHP


1
OOP with PHP
  • Roman Bednarik
  • rbednari_at_cs.joensuu.fi

2
OOP with PHPlecture outline
  • What is PHP
  • Why use OOP with PHP
  • OOP with PHP
  • Advanced topics on OOP and PHP

3
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

4
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

5
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

6
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
7
OOP with PHPlecture outline
  • What is PHP
  • Why use OOP with PHP
  • OOP with PHP
  • Advanced topics on OOP and PHP

8
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!

9
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

10
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

11
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'

12
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

13
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

14
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

15
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

16
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

17
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

18
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

19
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.

20
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()

21
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

22
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

23
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

24
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"

25
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

26
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

27
OOP with PHPlecture outline
  • What is PHP
  • Why use OOP with PHP
  • OOP with PHP
  • Advanced topics on OOP and PHP

28
OOP with PHP
  • Generic function for setting the member variables
  • function Set (varname, value)
  • this-gtvarname value
  • instance-gtSet ('size','5')

29
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!

30
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

31
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

32
(No Transcript)
33
  • USE OOP!
  • Thank you
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