oop with php - joensuucs.joensuu.fi/pages/bednarik/oop/oophp.pdf · oop with php what is php? -...
TRANSCRIPT
OOP with PHPlecture outline
What is PHP Why use OOP with PHP OOP with PHP Advanced topics on OOP and PHP
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
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
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
OOP with PHPwhat is PHP? - example
Browser view
Result of 1+2 =3Hello world!
PHP source (example.php)
<html><body>
<?php
$A = 1;$B = 2;$C = $A + $B;
echo “Result of $A+$B=”.$C;echo “<BR>\n”;echo “Hello world!”;
?>
</body></html>
OOP with PHPlecture outline
What is PHP Why use OOP with PHP OOP with PHP Advanced topics on OOP and PHP
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!
OOP with PHPwhy OOP in PHP – examples
Online shops Banking systems News services Editors' systems Home pages => use OOP to separate the functionality from
layout
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
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'
OOP with PHPcase class
<?php
class FirstClass {var $x; // data member – no ways of specifying private/protected
function setX ($a) {
$this->x = $a;}
function getX () {return $this->x;
}
function printX(){ echo $this->x;}
} // class
$instanceA = new FirstClass;?>
OOP with PHPAbstract data types
Both we have in PHP classes:
– Data : integer, string, array, associative array, object
– In PHP: no data protection, public is default
– Methods: defined as a member functionse.g: function setData1 ($aData1=”default”) { $this -> Data1 = $aData1; }
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
OOP with PHPInheritance
In PHP using keyword extends<?php
class SecondClass extends FirstClass{var $Y;function setY ($a) { if ( getX()>0) $this->Y = $a; // getX inherited else $this->Y = 0;}
}?> Multiple inheritance is not supported
OOP with PHPPolymorphism
All class member functions are virtual by the definition
class A {
function draw() { echo "1"; } // not needed
function boo() { $this->draw(); }
}
class B extends A {
function draw() { echo "drawing B"; }
}
$b = new B();
$b->boo(); // outputs “drawing B”
OOP with PHPconstructors
All initialization has to be done in constructor No constructor chaining! => 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
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
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.:
OOP with PHPstatic variables
$GLOBALS['_transient']['static']['test']->v1 = 1; // global storage
class Test {
function Test() { // constructor
$this->v1 = & $GLOBALS['_transient']['static']['test']->v1; // link a new variable
}
function printAndIncrease() {
echo "$this->v1 <br>";
$this->v1++;
}
var $v1;
}
$test1 = new Test(); // invokes constructor
$test1->printAndIncrease();
$test2 = new Test();
$test2->printAndIncrease();
OOP with PHPPHP fails on
No templates No private/protected members No casting from one class to another No static class variables No interfaces No exceptions => many to be resolved in PHP5
OOP with PHP<?php
class Element{ //basic class for all elements
function Element($caption=""){
$this->Setup($caption);
}
function Setup($caption) {
$this->caption = $caption;
}
function Set(){ //virtual methods
}
function Get(){ }
function GetCaption(){
return $this->caption;
}
function Print_(){}
}
?>
OOP with PHP<?php
include_once("class.element.php");
class Button extends Element { //inheritance
function Button($caption="",$action=""){
$this->Setup($caption,$action);
}
function Setup($caption,$action) {
$this->caption = $caption;
$this->action = $action;
}
function Print_() {
echo "<INPUT TYPE=button ";
if ($this->caption) echo "VALUE=\"$this->caption\" ";
if ($this->action) echo "OnClick=\"$this->action\" ";
echo ">\n";
}
}
?>
OOP with PHP<?php
include_once("class.element.php"); include_once("class.button.php");
class Page{
var $reload;
function Page($caption="",$obj){
$this->Setup($caption,$obj);
//add the properties and elements common to all pages
$this->reload = new Button("Reload","document.location.reload();");
}
function Setup($caption, $obj) {
$this->caption = $caption;
$this->obj = $obj;
}
function GetCaptions() {
for ($i=0; $i< count($this->obj); $i++) {
echo $this->obj[$i]->GetCaption(); echo "<BR>";}
}
OOP with PHP function print_(){
echo "<HTML>\n <HEAD>\n <TITLE>";
if ($this->caption) echo "$this->caption";
echo " </TITLE>\n";
echo " </HEAD>\n";
echo " <BODY>\n";
$this->reload->Print_();
for ($i=0; $i< count($this->obj); $i++) { //invoke Print_() for all
//elements on page
$this->obj[$i]->Print_();
echo "<BR>";
}
echo " </BODY>\n";
echo "</HTML>\n";
}
}
?>
OOP with PHPhttp://cs.joensuu.fi/pages/bednarik/OOP/example.php
<?php
include("class.element.php");include("class.button.php");
include("class.table.php");include("class.page.php");
$tab= new Table();
$tab->Setup("My table 10x3",10,3);
$tab2= $tab;
$tab2->Setup("My table 2 3x3",3,3);
$but = new Button("Click me","alert('Hello');");
$obs[0] = $tab;
$obs[1] = $tab2;
$obs[2] = $but;
$page= new Page("Object Page",$obs);
$page->Print_();
$page->GetCaptions();
?>
OOP with PHPlecture outline
What is PHP Why use OOP with PHP OOP with PHP Advanced topics on OOP and PHP
OOP with PHP
Generic function for setting the member variables
function Set ($varname, $value) {
$this->$varname = $value;}
$instance->Set ('size','5');
OOP with PHPSerializing the objects
Partially overcomes the need for a persistent object !!Saves only data members, not methods! (PHP4 is
exception)<?php
$myCart = new ShoppingCart();
$stream1 = serialize($myCart); // and store to file or db
...
... // retreive from file/db after a year..
$myLaterCart = unserialize($stream1);
?>
Not recommended to use!
OOP with PHPOverloading in PHP
<?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);
$run = “\$this->$to_call ($args);”; // variable variable
eval ($run);
}
function ShoppingCart1($x=”2”) { code1();}
function ShoppingCart2($x=”2”,$y=”3”) { code2();}
}
?>
OOP with PHPSerializing the objects (cont.)
Stream is a string with defined format One might try to investigate it:$myCart = new ShoppingCart();
$stream1 = serialize($myCart);
$hocus = explode(':',$stream1); // split $stream1 by : into array
e.g.
$classname = str_replace( “\””, '' ,$hocus[2] ); // takes away the “
USE OOP!
Thank you