php chapter10

8/20/2019 PHP Chapter10

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Chapter 10

Developing

Object-Oriented PHP


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Objectives

In this chapter, you ill!

" #tudy object-oriented progra$$ing concepts

" %se objects in PHP scripts

" Declare data $e$bers in classes

" &or' ith class $e$ber (unctions


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)

Introduction to Object-OrientedProgra$$ing

" Object-oriented programming *OOP+ re(ersthe concept o( $erging related variables and(unctions into a single inter(ace

" n object re(ers to progra$$ing code and datathat can be treated as an individual unit orco$ponent

"Objects are o(ten also called components


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Introduction to Object-OrientedProgra$$ing *continued+

" Data re(ers to in(or$ation contained ithinvariables or other types o( storage structures

" .he (unctions associated ith an object are

called methods" .he variables that are associated ith an object

are called properties or attributes

" Popular object-oriented progra$$ing languagesinclude C//, ava, and isual asic


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Introduction to Object-OrientedProgra$$ing *continued+

Figure 10-1 Accounting program


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%nderstanding 5ncapsulation

" Objects are encapsulated 6 all code andre7uired data are contained ithin the objectitsel(

" 5ncapsulated objects hide all internal codeand data

" n interface re(ers to the $ethods andproperties that are re7uired (or a sourceprogra$ to co$$unicate ith an object


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%nderstanding 5ncapsulation*continued+

" 5ncapsulated objects allo users to see only the$ethods and properties o( the object that youallo the$ to see

" 5ncapsulation reduces the co$ple9ity o( thecode

" 5ncapsulation prevents other progra$$ers (ro$accidentally introducing a bug into a progra$, orstealing code


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Object-Oriented Progra$$ingand Classes

" .he code, $ethods, attributes, and otherin(or$ation that $a'e up an object areorgani;ed into classes

" n instance is an object that has been created(ro$ an e9isting class

" Creating an object (ro$ an e9isting class iscalled instantiating the object

" n object inherits its $ethods and properties(ro$ a class < it ta'es on the characteristics o(the class on hich it is based


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%sing Objects in PHP #cripts

" Declare an object in PHP by using the new operator ith a class constructor

" class constructor is a special (unction ith

the sa$e na$e as its class that is calledauto$atically hen an object (ro$ the class isinstantiated

" .he synta9 (or instantiating an object is!

$ObjectName = new ClassName();


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%sing Objects in PHP #cripts*continued+

" (ter an object is instantiated, use a hyphen anda greater-than sy$bol *->+ to access the$ethods and properties contained in the object

" .ogether, these to characters are re(erred to asmember selection notation

" &ith $e$ber selection notation, one or $orecharacters are appended to an object, (olloedby the na$e o( a $ethod or property


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%sing Objects in PHP #cripts*continued+

" &ith $ethods, include a set o( parentheses atthe end o( the $ethod na$e, just as ith(unctions

" >i'e (unctions, $ethods can also acceptargu$ents

$Checking->getBalance();

$CheckNumber = 1022;

$Checking->getCheckAmount($CheckNumber);


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&or'ing ith DatabaseConnections as Objects

" ccess ?y#@> database connections as objectsby instantiating an object (ro$ the m!"li class

" .o connect to a ?y#@> database server using

procedural synta9! $#BConnect = m!"lconnect(%&h&'b% %'ongo!!elin%

%ro!ebu'%);

m!"l!elect'b(%reale!tate% $#BConnect);

" .o connect to the ?y#@> database server usingobject-oriented style!

$#BConnect = new m!"li(%&h&'b% %'ongo!!elin%

%ro!ebu'% %reale!tate%);


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Handling ?y#@> 5rrors

" .his state$ent uses the m!"li() constructor(unction to instantiate a m!"li class objectna$ed $#BConnect

$#BConnect = new m!"li(%&h&'b% %'go!!elin%%ro!ebu'%);

" .o e9plicitly close the database connection, usethe clo!e() $ethod o( the m!"li class $#BConnect->clo!e();


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Handling ?y#@> 5rrors *continued+

" &ith object-oriented style, chec' hether a valueis assigned to the m!"liconnecterrno() or m!"liconnecterror() (unctions

$#BConnect = new m!"li(%&h&*'b% %'go!!elin% %ro!ebu'%);

i+ ($#BConnect->connecterrno),

echo(%&>.nable to connect to the 'ataba!e!er/er*&>%

* %&>rror co'e % * $#BConnect->connecterrno

* % % * $#BConnect->connecterror* %&>3n%;

el!e ,co'e to e4ecute i+ the connection +ail!

5


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59ecuting #@> #tate$ents

" &ith object-oriented style, use the "uer() $ethod o( the m!"li class

" .o return the (ields in the current ro o( a resultset

into an inde9ed array use! 6 .he +etchrow() $ethod o( the m!"li class

" .o return the (ields in the current ro o( a resultsetinto an associative array use!

6 .he +etcha!!oc() $ethod o( the m!"li class


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59ecuting #@> #tate$ents*continued+

$6ableName = %com&ancar!%;

$789!tring = %79C6 : % *

%th>ileageth>th>earth>tr>3n%;


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59ecuting #@> #tate$ents*continued+

A

while (($t'>,$,$,$,$,$


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De(ining Custo$ PHP Classes

" Data structure re(ers to a syste$ (or organi;ingdata

" .he (unctions and variables de(ined in a class

are called class members" Class variables are re(erred to as data

members or member variables

" Class (unctions are re(erred to as member functions or function members


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De(ining Custo$ PHP Classes*continued+

" Classes! 6 Help $a'e co$ple9 progra$s easier to $anage

6 Hide in(or$ation that users o( a class do not need

to access or 'no about 6 ?a'e it easier to reuse code or distribute your

code to others (or use in their progra$s

" Inherited characteristics allo you to build ne

classes based on e9isting classes ithouthaving to rerite the code contained in thee9isting one


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Creating a Class De(inition

" .o create a class in PHP, use the cla!! 'eyord to rite a class de(inition

" class definition contains the data $e$bers

and $e$ber (unctions that $a'e up the class" .he synta9 (or de(ining a class is!

cla!! ClassName ,

data member and member function definitions5


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Creating a Class De(inition*continued+

" .he ClassName portion o( the class de(inition isthe na$e o( the ne class

" Class na$es usually begin ith an uppercase

letter to distinguish the$ (ro$ other identi(iers" &ithin the classBs curly braces, declare the data

type and (ield na$es (or each piece o(in(or$ation stored in the structure

cla!! BankAccount , data member and member function definitions

5

$Checking = new BankAccount();


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Creating a Class De(inition*continued+

" Class na$es in a class de(inition are not(olloed by parentheses, as are (unctionna$es in a (unction de(inition

$Checking = new BankAccount();echo ?6he $Checking obGect i! in!tantiate' +rom the ?

* get_class($Checking) * % cla!!*&>%;

" %se the in!tanceo+ operator to deter$inehether an object is instantiated (ro$ a given

class" %se the cla!!e4i!t!() to deter$ine i( a

class e9ists


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#toring Classes in 59ternal iles

" PHP provides the (olloing (unctions that alloyou to use e9ternal (iles in your PHP scripts!H inclu'e()

H re"uire()H inclu'eonce()

H re"uireonce()

" ou pass to each (unction the na$e and path o(the e9ternal (ile you ant to use


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#toring Classes in 59ternal iles*continued+

I inclu'e() and re"uire() (unctions bothinsert the contents o( an e9ternal (ile, called aninclude file, into a PHP script

I inclu'eonce() and re"uireonce() (unctions only include an e9ternal (ile onceduring the processing o( a script

" ny PHP code $ust be contained ithin a PHPscript section *J&h& *** J>) in an e9ternal(ile


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Collecting Earbage

" Garbage collection re(ers to cleaning up orreclai$ing $e$ory that is reserved by aprogra$

" PHP 'nos hen your progra$ no longer needsa variable or object and auto$atically cleans upthe $e$ory (or you

" .he one e9ception is ith open databaseconnections


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In(or$ation Hiding

" Information hiding states that any class$e$bers that other progra$$ers, so$eti$escalled clients, do not need to access or 'noabout should be hidden

" Helps $ini$i;e the a$ount o( in(or$ation thatneeds to pass in and out o( an object

" Feduces the co$ple9ity o( the code that clientssee

" Prevents other progra$$ers (ro$ accidentallyintroducing a bug into a progra$ by $odi(ying aclassBs internal or'ings


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%sing ccess #peci(iers

" Access specifiers control a clientBs access toindividual data $e$bers and $e$ber (unctions

" .here are three levels o( access speci(iers in

PHP! &ublic, &ri/ate, and &rotecte'" .he public access specifier allos anyone tocall a classBs $e$ber (unction or to $odi(y andretrieve a data $e$ber


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%sing ccess #peci(iers*continued+

" .he private access specifier prevents clients(ro$ calling $e$ber (unctions or accessing data$e$bers and is one o( the 'ey ele$ents inin(or$ation hiding

" Private access does not restrict a classBs internalaccess to its on $e$bers

" Private access restricts clients (ro$ accessing

class $e$bers


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%sing ccess #peci(iers*continued+

" Include an access speci(ier at the beginning o( adata $e$ber declaration state$ent

cla!! BankAccount ,

public $Balance = 0;

5

" lays assign an initial value to a data $e$berhen you (irst declare it

cla!! BankAccount ,

&ublic $Balance = 1 K 2;

5


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#eriali;ing Objects

" Serialiation re(ers to the process o( convertingan object into a string that you can store (orreuse

" #eriali;ation stores both data $e$bers and$e$ber (unctions into strings

" .o seriali;e an object, pass an object na$e tothe !erialiLe() (unction

$7a/e'Account = !erialiLe($Checking);


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#eriali;ing Objects *continued+

" .o convert seriali;ed data bac' into an object,you use the un!erialiLe() (unction

$Checking = un!erialiLe($7a/e'Account);

" #eriali;ation is also used to store the data inlarge arrays

" .o use seriali;ed objects beteen scripts, assigna seriali;ed object to a session variable

!e!!ion!tart();

$777MN(?7a/e'Account?) = !erialiLe($Checking);


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&or'ing ith ?e$ber unctions

" Create public $e$ber (unctions (or any(unctions that clients need to access

" Create private $e$ber (unctions (or any

(unctions that clients do not need to access" ccess speci(iers control a clientBs access to

individual data $e$bers and $e$ber (unctions


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&or'ing ith ?e$ber unctions*continued+

cla!! BankAccount ,&ublic $Balance = OP*20;

public function withdrawal($Amount) {

$this->alance -! $Amount"

#

5

i+ (cla!!e4i!t!(%BankAccount%))


el!e

e4it(%&>6he BankAccount cla!! i! not a/ailable&>%);

&rint+(%&>our checking account balance i! $@*2+*&>%

$Checking->Balance);

$Ca!h = 200;

$Checking->withdrawal(%%)"

&rint+(%&>A+ter with'rawing $@*2+ our checking account balance

i! $@*2+*&>% $Ca!h $Checking->Balance);


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%sing the $thi! Fe(erence

" Outside o( a class, re(er to the $e$bers o( theobject using the na$e o( the object, the $e$berselection nation *-+, and the na$e o( the (unctionor variable

" &ithin a class (unction de(inition, use Gthis tore(er to the current object o( the class

$thi!->AccountNumber = 0;


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Initiali;ing ith Constructorunctions

" constructor function is a special (unction thatis called auto$atically hen an object (ro$ aclass is instantiatedcla!! BankAccount ,

&ri/ate $AccountNumber;

&ri/ate $Cu!tomerName;

&ri/ate $Balance;

+unction con!truct() ,

$thi!->AccountNumber = 0;

$thi!->Balance = 0;

$thi!->Cu!tomerName = %%;

5

5


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Initiali;ing ith Constructorunctions *continued+

" .he con!truct() (unction ta'esprecedence over a (unction ith the sa$e na$eas the class

" Constructor (unctions are co$$only used inPHP to handle database connection tas's


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Cleaning %p ith Destructorunctions

" de(ault constructor (unction is called hen aclass object is (irst instantiated

" destructor (unction is called hen the object

is destroyed" destructor (unction cleans up any resources

allocated to an object a(ter the object isdestroyed


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Cleaning %p ith Destructorunctions *continued+

" destructor (unction is co$$only called in toays!

6 &hen a script ends

6 &hen you $anually delete an object iththe un!et() (unction

" .o add a destructor (unction to a PHP class,create a (unction na$ed 'e!truct()


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Cleaning %p ith Destructorunctions *continued+

+unction con!truct() ,

$#BConnect = new m!"li(%&h&'b%

%'ongo!!elin%%ro!ebu'%

%reale!tate%);

5

function __destruct() {

$&Connect->close()"

#


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&riting ccessor unctions

" Accessor functions are public $e$ber(unctions that a client can call to retrieve or$odi(y the value o( a data $e$ber

" ccessor (unctions o(ten begin ith the ordsset or get

" #et (unctions $odi(y data $e$ber values

"Eet (unctions retrieve data $e$ber values


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&riting ccessor unctions*continued+

cla!! BankAccount ,

&ri/ate $Balance = 0;

&ublic +unction !etBalance($NewQalue) ,

$thi!->Balance = $NewQalue;

5

&ublic +unction getBalance() ,

return $thi!->Balance;5

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i+ (cla!!e4i!t!(%BankAccount%))


el!e

e4it(%&>6he BankAccount cla!! i! not a/ailable&>%);

$Checking->!etBalance(100);

echo %&>our checking account balance i! %

* $Checking->getBalance() * %&>3n%;


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#eriali;ation unctions

" &hen you seriali;e an object ith the!erialiLe() (unction, PHP loo's in theobjectBs class (or a special (unction na$ed

!lee&()" .he pri$ary reason (or including a !lee&()

(unction in a class is to speci(y hich data$e$bers o( the class to seriali;e


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#eriali;ation unctions *continued+

" I( you do not include a !lee&() (unction inyour class, the !erialiLe() (unction seriali;esall o( its data $e$bers

+unction !lee&() ,

$7erialQar! = arra(?Balance?);

return $7erialQar!;

5

" &hen the un!erialiLe() (unction e9ecutes,

PHP loo's in the objectBs class (or a special(unction na$ed wakeu&()


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#u$$ary

" .he ter$ object-oriented programming*OOP+ re(ers to the creation o( reusableso(tare objects that can be easily incorporated

into $ultiple progra$sJ .he ter$ objectspeci(ically re(ers to progra$$ing code and datathat can be treated as an individual unit orco$ponent *object+

" .he ter$ data re(ers to in(or$ation containedithin variables or other types o( storagestructures


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#u$$ary *continued+

" In object-oriented progra$$ing, the code,$ethods, attributes, and other in(or$ation that$a'e up an object are organi;ed into classes

" n instance is an object that has been created(ro$ an e9isting classJ &hen you create anobject (ro$ an e9isting class, you areinstantiating the object”


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#u$$ary *continued+

" particular instance o( an object inherits its$ethods and properties (ro$ a class


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#u$$ary *continued+

" .he (unctions and variables de(ined in a classare called class membersJ Class variables arere(erred to as data members or member

variables, hereas class (unctions are re(erredto as member functions or (unction members

" class definition contains the data $e$bersand $e$ber (unctions that $a'e up the class


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#u$$ary *continued+

" PHP provides the (olloing (unctions that alloyou to use e9ternal (iles in your PHP scripts!inclu'e(), re"uire(), inclu'eonce(),

and re"uireonce()" .he principle o( information hiding states that

class $e$bers should be hidden hen otherprogra$$ers do not need to access or 'no

about the$" Access specifiers control a clientBs access to

individual data $e$bers and $e$ber (unctions


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#u$$ary *continued+

" Serialiation re(ers to the process o( convertingan object into a string that you can store (orreuse

" constructor function is a special (unction thatis called auto$atically hen an object (ro$ aclass is instantiated

" destructor function cleans up any resources

allocated to an object a(ter the object isdestroyed


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#u$$ary *continued+

" Accessor functions are public $e$ber(unctions that a client can call to retrieve thevalue o( a data $e$ber

" !utator functions are public $e$ber (unctionsthat a client can call to $odi(y the value o( adata $e$ber


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#u$$ary *continued+

" &hen you seriali;e an object ith the!erialiLe() (unction, PHP loo's in theobjectBs class (or a special (unction na$ed

!lee&(), hich you can use to per(or$$any o( the sa$e tas's as a destructor (unction

" &hen the un!erialiLe() (unction e9ecutes,PHP loo's in the objectBs class (or a special

(unction na$ed wakeu&(), hich you canuse to per(or$ $any o( the sa$e tas's as aconstructor (unction

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