A little abstraction abst r act cl ass Hum ans { publ i c f unct i on __const r uct ( $nam e) { / * . . . * / } abst r act publ i c f unct i on gender ( ) ; publ i c f unct i on eat ( ) { / * . . . * / } publ i c f unct i on sl eep( ) { / * . . . * / } publ i c f unct i on wakeup( ) { / * . . . * / } } cl ass W om en ext ends Hum ans { publ i c f unct i on gender ( ) { r et ur n ' f em al e' ; } publ i c f unct i on gi veBi r t h( ) { / * . . . * / } } cl ass M en ext ends Hum ans { publ i c f unct i on gender ( ) { r et ur n ' m al e' ; } publ i c f unct i on snor e( ) { / * . . . * / } } Marcus Börger Introduction to Object-oriented programming with PHP 23
A little abstraction abst r act cl ass Hum ans { publ i c f unct i on __const r uct ( $nam e) { / * . . . * / } abst r act publ i c f unct i on gender ( ) ; publ i c f unct i on eat ( ) { / * . . . * / } publ i c f unct i on sl eep( ) { / * . . . * / } publ i c f unct i on wakeup( ) { / * . . . * / } } cl ass W om en ext ends Hum ans { f i nal publ i c f unct i on gender ( ) { r et ur n ' f ' ; } publ i c f unct i on gi veBi r t h( ) { / * . . . * / } } cl ass M en ext ends Hum ans { f i nal publ i c f unct i on gender ( ) { r et ur n ' m ' ; } publ i c f unct i on snor e( ) { / * . . . * / } } Marcus Börger Introduction to Object-oriented programming with PHP 24
PHP and OOP Marcus Börger Introduction to Object-oriented programming with PHP 25
PHP 4 and OOP ? � Poor Object model � Methods � No visibility � No abstracts, no final � Static without declaration � Properties � No static properties � No constants � Inheritance � No abstract, final inheritance, no interfaces � No prototype checking, no types � Object handling � Copied by value � No destructors Marcus Börger Introduction to Object-oriented programming with PHP 26
ZE2's revamped object model � Objects are referenced by identifiers � Constructors and Destructors � Static members � Constants � Visibility � Interfaces � Final and abstract members � Interceptors � Exceptions � Reflection API � Iterators Marcus Börger Introduction to Object-oriented programming with PHP 27
Revamped Object Model � PHP 5 has really good OOP support � Better code reuse � Better for team development � Easier to refactor � Some patterns lead to much more efficient code � Fits better in marketing scenarios Marcus Börger Introduction to Object-oriented programming with PHP 28
PHP 5 OOP in detail Marcus Börger Introduction to Object-oriented programming with PHP 29
Objects referenced by identifiers � Objects are no longer somewhat special arrays � Objects are no longer copied by default � Objects may be copied using clone/ __clone() cl ass O bj ect { } ; $obj $ref $dup $obj = new O bj ect ( ) ; Instance 1 Instance 2 $r ef = $obj ; $dup = cl one cl one $obj ; Class Object Marcus Börger Introduction to Object-oriented programming with PHP 30
Constructors and Destructors � Constructors/ Destructors control object lifetime � Constructors may have both new OR old style name � New style constructors are preferred � Constructors must not use inherited protocol � Destructors are called when deleting the last reference � No particular or controllable order during shutdown � Destructors cannot have parameters � Since PHP 5.0.1 destructors can work with resources cl ass O bj ect { f unct i on __const r uct __const r uct ( ) { } f unct i on __dest r uct __dest r uct ( ) { } } $obj = new O bj ect ( ) ; unset ( $obj ) ; Marcus Börger Introduction to Object-oriented programming with PHP 31
Constructors and Destructors � Parents must be called manually cl ass Base { f unct i on __const r uct ( ) { } f unct i on __dest r uct ( ) { } } cl ass O bj ect ext ends Base { f unct i on __const r uct ( ) { par ent par ent : : __const r uct ( ) ; } f unct i on __dest r uct ( ) { par ent par ent : : __dest r uct ( ) ; } } $obj = new O bj ect ( ) ; unset ( $obj ) ; Marcus Börger Introduction to Object-oriented programming with PHP 32
Default property values � Properties can have default values � Bound to the class not to the object � Default values cannot be changed but overwritten cl ass O bj ect { $obj1 $obj2 var $pr op = " Hel l o\ n" ; } Instance 1 Instance 2 $prop $prop $obj 1 = new O bj ect ; $obj 1- >pr op = " Hel l o W or l d\ n" ; Class Object $obj 2 = new O bj ect ; $prop/default echo $obj 2- >pr op; / / Hel l o Marcus Börger Introduction to Object-oriented programming with PHP 33
Static members � Static methods and properties � Bound to the class not to the object � Only exists once per class rather than per instance � Can be initialized $obj1 $obj2 cl ass O bj ect { Instance 1 Instance 2 var $pr op; $prop $prop st at i c st at i c $st at = " Hel l o\ n" ; st at i c st at i c f unct i on t est ( ) { echo sel f sel f : : $st at ; } Class Object } $stat O bj ect : : t est ( ) ; $obj 1 = new O bj ect ; $obj 2 = new O bj ect ; Marcus Börger Introduction to Object-oriented programming with PHP 34
Pseudo constants � __CLASS__ __CLASS__ shows the current class name � __M __M ETHO ETHO D__ D__ shows class and method or function � sel f sel f references the class itself � par ent par ent references the parent class � $t hi s $t hi s references the object itself cl ass Base { st at i c f unct i on Show( ) { echo __FI LE__. ' ( ' . __LI NE__. ' ) : ' . __M ETHO D__. " \ n" ; } } cl ass O bj ect ext ends Base { st at i c f unct i on Use( ) { Sel f : : Show( ) ; Par ent : : Show( ) ; } st at i c f unct i on Show( ) { echo __FI LE__. ' ( ' . __LI NE__. ' ) : ' . __M ETHO D__. " \ n" ; } } Marcus Börger Introduction to Object-oriented programming with PHP 35
Visibility � Controlling member visibility / Information hiding � A derived class doesn't know parents private members � An inherited protected member can be made public cl ass Base { publ i c publ i c $a; Derived pr ot ect ed $b; pr ot ect ed Base pr i vat e $c; pr i vat e $a } $b cl ass Der i ved ext ends Base { $c publ i c publ i c $a; publ i c publ i c $b; $a pr i vat e pr i vat e $c; $b } $c Base::$c Marcus Börger Introduction to Object-oriented programming with PHP 36
Constructor visibility � A protected constructor prevents instantiation cl ass Base { pr ot ect ed f unct i on __const r uct ( ) { } } cl ass Der i ved ext ends Base { / / const r uct or i s st i l l pr ot ect ed st at i c f unct i on get Base( ) { r et ur n new Base; / / Fact or y pat t er n } } cl ass Thr ee ext ends Der i ved { publ i c f unct i on __const r uct ( ) { } } Marcus Börger Introduction to Object-oriented programming with PHP 37
The Singleton pattern � Sometimes you want only a single instance of aclass to ever exist. � DB connections � An object representing the user or connection. cl ass Si ngl et on { st at i c pr i vat e $i nst ance; pr ot ect ed f unct i on __const r uct ( ) { } f i nal pr i vat e f unct i on __cl one( ) { } st at i c f unct i on get I nst ance( ) { i f ( ! sel f : : $i nst ance) sel f : : $i nst ance = new Si ngl et on( ) ; r et ur n sel f : : $i nst ance; } } $a = Si ngl et on: : get I nst ance( ) ; $a- >i d = 1; $b = Si ngl et on: : get I nst ance( ) ; pr i nt $b- >i d. " \ n" ; Marcus Börger Introduction to Object-oriented programming with PHP 38
Constants � Constants are read only static properties � Constants are always public cl ass Base { const const gr eet i ng = " Hel l o\ n" ; } cl ass Der vi ed ext ends Base { const const gr eet i ng = " Hel l o W or l d\ n" ; st at i c f unct i on f unc( ) { echo par ent : : gr eet i ng; } } echo Base: : gr eet i ng; echo Der i ved: : gr eet i ng; Der i ved: : f unc( ) ; Marcus Börger Introduction to Object-oriented programming with PHP 39
Abstract members � Methods can be abstract � They don’t have a body � A class with an abstract method must be abstract � Classes can be made abstract � The class cannot be instantiated � Properties cannot be made abstract abst r act abst r act cl ass Base { abst r act abst r act f unct i on no_body( ) ; } cl ass Der i ved ext ends Base { f unct i on no_body( ) { echo " Body\ n" ; } } Marcus Börger Introduction to Object-oriented programming with PHP 40
Final members � Methods can be final � They cannot be overwritten � They are class invariants � Classes can be final � They cannot be inherited cl ass Base { f i nal f i nal f unct i on i nvar i ant ( ) { echo " Hel l o\ n" ; } } cl ass Der i ved ext ends Base { } f i nal f i nal cl ass Leaf ext ends Der i ved { } Marcus Börger Introduction to Object-oriented programming with PHP 41
Different Object same behavior � Often different objects have the same interface without having the same base class cl ass Li ne { f unct i on dr aw( ) { } ; } cl ass Pol ygon { pr ot ect ed $l i nes; f unct i on dr aw( ) { Line Ellipse f or each( $t hi s- >l i nes as $l i ne) $l i ne- >dr aw( ) ; } } $lines cl ass Rect angl e ext ends Pol ygon { } Circle Polygon cl ass El l i pse { f unct i on dr aw( ) { } ; } cl ass Ci r cl e ext ends El l i pse { f unct i on dr aw( ) { par ent : : dr aw( ) ; Rectangle } } Marcus Börger Introduction to Object-oriented programming with PHP 42
Interfaces � Interfaces describe an abstract class protocol � Classes may inherit multiple Interfaces i nt er f ace Dr awabl e { f unct i on dr aw( ) ; } Drawable cl ass Li ne i m pl em ent s Dr awabl e { f unct i on dr aw( ) { } ; } cl ass Pol ygon i m pl em ent s Dr awabl e { pr ot ect ed $l i nes; f unct i on dr aw( ) { Line Ellipse f or each( $t hi s- >l i nes as $l i ne) $l i ne- >dr aw( ) ; } } $lines cl ass Rect angl e ext ends Pol ygon { } Circle Polygon cl ass El l i pse i m pl em ent s Dr awabl e { f unct i on dr aw( ) { } ; } cl ass Ci r cl e ext ends El l i pse { f unct i on dr aw( ) { par ent : : dr aw( ) ; Rectangle } } Marcus Börger Introduction to Object-oriented programming with PHP 43
Property kinds � Declared properties � May have a default value � Can have selected visibility � Implicit public properties � Declared by simply using them in ANY method � Virtual properties � Handled by interceptor methods � Static properties � Bound to the class rather than to the instance Marcus Börger Introduction to Object-oriented programming with PHP 44
Object to String conversion � __toString(): semi-automatic object to string conversion with echo and print (automatic starting with 5.2) cl ass O bj ect { f unct i on __t oSt r i ng __t oSt r i ng( ) { r et ur n ' O bj ect as st r i ng' ; } } $o = new O bj ect ; echo $o; / / does cal l __t oSt r i ng $st r = ( st r i ng) $o; / / does cal l __t oSt r i ng Marcus Börger Introduction to Object-oriented programming with PHP 45
Interceptors � Allow to dynamically handle non class members � Lazy initialization of properties � Simulating Object aggregation and Multiple inheritance cl ass O bj ect { pr ot ect ed $vi r t ual = ar r ay( ) ; f unct i on __get __get ( $nam e) { r et ur n @ $t hi s- >vi r t ual [ $nam e] ; } f unct i on __set __set ( $nam e, $val ue) { $t hi s- >vi r t ual [ $nam e] = $val ue; } f unct i on __unset __unset ( $nam e) { unset ( $t hi s- >vi r t ual [ $nam e] ) ; } f unct i on __i sset __i sset ( $nam e) { r et ur n i sset ( $t hi s- >vi r t ual [ $nam e] ) ; } f unct i on __cal l __cal l ( $f unc, $par am s) { echo ' Coul d not cal l ' . __CLASS__ . ' : : ' . $f unc . " \ n" ; } } Marcus Börger Introduction to Object-oriented programming with PHP 46
Typehinting � PHP 5 allows to easily force a type of a parameter � PHP does not allow NULL for typehints � Typehints must be inherited as given in base class � PHP 5.1 offers typehinting with arrays � PHP 5.2 offers optional typehinted parameters (= NULL) cl ass O bj ect { publ i c f unct i on com par e( O bj ect $ot her ) { / / Som e code her e } publ i c f unct i on com par e2( $ot her ) { i f ( i s_nul l ( $ot her ) | | $ot her i nst anceof O bj ect ) { / / Som e code her e } } } Marcus Börger Introduction to Object-oriented programming with PHP 47
Class Design � It is important to think about your class hierarchy � Avoid very deep or broad inheritance graphs � PHP only supports is-a and has-a relations Tires Bicycle Vehicle Engine Car Bus Truck Diesel Gasoline Tank Turbine Plane Marcus Börger Introduction to Object-oriented programming with PHP 48
Too Strict or too Weak? � PHP tries to prevent you from doing some errors � You are bound to keep inherited signatures � You cannot change from ref to non-ref return � Yet PHP allows absolute flexibility � Just do not define a signature � Warning: This is extremely error prone Marcus Börger Introduction to Object-oriented programming with PHP 49
Dynam ic class loading Marcus Börger Introduction to Object-oriented programming with PHP 50
Dynamic class loading � � __aut ol oad( ) is good __aut ol oad( ) is good when you're alone � Requires a single file for each class � Only load class files when necessary � No need to parse/ compile unneeded classes � No need to check which class files to load � Additional user space code � Only one single loader model is possible Marcus Börger Introduction to Object-oriented programming with PHP 51
__aut ol oad & r equi r e_once � St or e t he cl ass l oader i n an i ncl ude f i l e � I n each scr i pt : r equi r e_once( ' <pat h>/ aut ol oad. i nc' ) � Use I NI opt i on: aut o_pr epend_f i l e=<pat h>/ aut ol oad. i nc <?php f unct i on __aut ol oad( $cl ass_nam e) { r equi r e_once( di r nam e( __FI LE__) . ' / ' . $cl ass_nam e . ' . p5c' ) ; } ?> Marcus Börger Introduction to Object-oriented programming with PHP 52
SPL's class loading � Supports fast default implementation � Look into path's specified by INI option include_path � Look for specified file extensions (.inc, .php) � Ability to register multiple user defined loaders � Overwrites ZEND engine's __autoload() cache � You need to register __autoload if using spl's autoload <?php spl _aut ol oad_r egi st er ( ' spl _aut ol oad' ) ; i f ( f unct i on_exi st s( ' __aut ol oad' ) ) { spl _aut ol oad_r egi st er ( ' __aut ol oad' ) ; } ?> Marcus Börger Introduction to Object-oriented programming with PHP 53
SPL's class loading � spl _aut ol oad( $cl ass_nam e, $ext ensi ons=NULL) Load a class from a file in include path Fast c code implementation � spl _aut ol oad_ext ensi ons( $ext ensi ons=NULL) Get or set filename extensions � spl _aut ol oad_r egi st er ( $l oader _f unct i on) Register a single loader function � spl _aut ol oad_unr egi st er ( $l oader _f unct i on) Unregister a single loader function � spl _aut ol oad_f unct i ons( ) List all registered loader functions � spl _aut ol oad_cal l ( $cl ass_nam e) Load a class through registered class loaders Uses spl _aut ol oad( ) as fallback Marcus Börger Introduction to Object-oriented programming with PHP 54
Exceptions Marcus Börger Introduction to Object-oriented programming with PHP 55
Exceptions � Respect these rules 1. Exceptions are exceptions 2. Never use exceptions for control flow 3. Never ever use exceptions for parameter passing <?php t r y { t r y / / your code t hr ow t hr ow new Except i on( ) ; } cat ch ( Except i on $e) { cat ch / / except i on handl i ng } ?> Marcus Börger Introduction to Object-oriented programming with PHP 56
Exception specialization � Exceptions should be specialized � Exceptions should inherit built in class exception cl ass Your Except i on ext ends Except i on { } t r y { / / your code t hr ow new Your Except i on( ) ; } cat ch ( Your Except i on $e) { / / except i on handl i ng } cat ch ( Except i on $e) { / / except i on handl i ng } Marcus Börger Introduction to Object-oriented programming with PHP 57
Exception specialization � Exception blocks can be nested � Exceptions can be re thrown cl ass Your Except i on ext ends Except i on { } t r y { t r y { / / your code t hr ow new Your Except i on( ) ; } cat ch ( Your Except i on $e) { / / except i on handl i ng t hr ow $e; } cat ch ( Except i on $e) { / / except i on handl i ng } } cat ch ( Your Except i on $e) { / / except i on handl i ng } Marcus Börger Introduction to Object-oriented programming with PHP 58
Practical use of exceptions � Constructor failure � Converting errors/ warnings to exceptions � Simplify error handling � Provide additional error information by tagging Marcus Börger Introduction to Object-oriented programming with PHP 59
Constructor failure � In PHP 4.4 you would simply unset ( $t hi s) � Provide an argument to receive the error condition <?php cl ass O bj ect { f unct i on __const r uct ( & $f ai l ur e) / / " O bj ect " i n PHP 4 { $f ai l ur e = t r ue; } } $er r or = f al se; $o = new O bj ect ( $er r or ) ; i f ( ! $er r or ) { / / er r or handl i ng, NO TE: t he obj ect was const r uct ed unset ( $o) ; } ?> Marcus Börger Introduction to Object-oriented programming with PHP 60
Constructor failure � In 5 constructors do not return the created object � Exceptions allow to handle failed constructors <?php cl ass O bj ect { f unct i on __const r uct ( ) { t hr ow new Except i on; } } t r y { $o = new O bj ect ; } cat ch ( Except i on $e) { echo " O bj ect coul d not be i nst ant i at ed\ n" ; } ?> Marcus Börger Introduction to Object-oriented programming with PHP 61
Convert Errors to Exceptions � Implementing PHP 5.1 class ErrorException <?php i f ( ! cl ass_exi st s( ' Er r or Except i on' , f al se) ) { cl ass Er r or Except i on ext ends Except i on { pr ot ect ed $sever i t y; f unct i on __const r uct ( $m sg, $code, $er r no, $f i l e, $l i ne) { par ent : : __const r uct ( $m sg, $code) ; $t hi s- >sever i t y = $er r no; $t hi s- >f i l e = $f i l e; $t hi s- >l i ne = $l i ne; } f unct i on get Sever i t y( ) { r et ur n $t hi s- >sever i t y; } } } ?> Marcus Börger Introduction to Object-oriented programming with PHP 62
Convert Errors to Exceptions � Implementing the error handler <?php f unct i on Er r or sToExcept i ons( $er r no, $m sg, $f i l e, $l i ne) { t hr ow new Er r or Except i on( $m sg, 0, $er r no, $f i l e, $l i ne) ; } set _er r or _handl er ( ' Er r or sToExcept i ons' ) ; ?> Marcus Börger Introduction to Object-oriented programming with PHP 63
Simplify error handling � Typical database access code contains lots of if's <ht m l ><body> <?php $ok = f al se; $db = new PDO ( ' CO NNECTI O N' ) ; i f ( $db) { $r es = $db- >quer y( ' SELECT dat a' ) ; i f ( $r es) { $r es2 = $db- >quer y( ' SELECT ot her ' ) ; i f ( $r es2) { / / handl e dat a $ok = t r ue; / / onl y i f al l went ok } } } i f ( ! $ok) echo ' <h1>Ser vi ce cur r ent l y unavai l abl e</ h1>' ; ?> </ body></ ht m l > Marcus Börger Introduction to Object-oriented programming with PHP 64
Simplify error handling � Trade code simplicity with a new complexity <ht m l ><body> <?php t r y { $db = new PDO ( ' CO NNECTI O N' ) ; $db- >set At t r i but e( PDO : : ATTR_ERRM O DE, PDO : : ERRM O DE_EXCEPTI O N) ; $r es = $db- >quer y( ' SELECT dat a' ) ; $r es2 = $db- >quer y( ' SELECT ot her ' ) ; / / handl e dat a } cat ch ( Except i on $e) { echo ' <h1>Ser vi ce cur r ent l y unavai l abl e</ h1>' ; er r or _l og( $e- >get M essage( ) ) ; } ?> </ body></ ht m l > Marcus Börger Introduction to Object-oriented programming with PHP 65
SPL Exceptions � SPL provides a standard set of exceptions � Class Exception must be the root of all exceptions Marcus Börger Introduction to Object-oriented programming with PHP 66
General distinguishing � Logi cExcept i on � Anything that could have been detected at compile time, during application design or by the good old technology: "look closely" � Runt i m eExcept i on � Anything that is unexpected during runtime � Base Exception for all database extensions Marcus Börger Introduction to Object-oriented programming with PHP 67
LogicException � Function not found or similar BadM et hodCal l Except i on � Value not in allowed domain � Argument not valid � Length exceeded � Some index is out of range Marcus Börger Introduction to Object-oriented programming with PHP 68
RunTimeException � An actual value is out of bounds � Buffer or other overflow situation � Value outside expected range � Buffer or other underflow situation � Any other unexpected values Marcus Börger Introduction to Object-oriented programming with PHP 69
Overloading __call � If using __call, ensure only valid calls are made abst r act cl ass M yI t er at or W r apper i m pl em ent s I t er at or { f unct i on __const r uct ( I t er at or $i t ) { Compile-Time: $t hi s- >i t = $i t ; } Error in design f unct i on __cal l ( $f unc, $ar gs) { $cal l ee = ar r ay( $t hi s- >i t , $f unc) ; i f ( ! i s_cal l abl e( $cal l ee) ) { t hr ow new BadM et hodCal l Except i on( ) ; } r et ur n cal l _user _f unc_ar r ay( $cal l ee, $ar gs) ; } } Marcus Börger Introduction to Object-oriented programming with PHP 70
Interfaces and __call � Interface functions cannot be handled by __call � Either mark the class abstract... abst r act cl ass M yI t er at or W r apper i m pl em ent s I t er at or { I nt er f ace I t er at or { f unct i on __const r uct ( I t er at or $i t ) f unct i on r ewi nd( ) ; { f unct i on val i d( ) ; $t hi s- >i t = $i t ; f unct i on cur r ent ( ) ; } f unct i on __cal l ( $f unc, $ar gs) f unct i on key( ) ; { f unct i on next ( ) ; $cal l ee = ar r ay( $t hi s- >i t , $f unc) ; } i f ( ! i s_cal l abl e( $cal l ee) ) { t hr ow new BadM et hodCal l Except i on( ) ; } r et ur n cal l _user _f unc_ar r ay( $cal l ee, $ar gs) ; } } Marcus Börger Introduction to Object-oriented programming with PHP 71
Interfaces and __call � Interface functions cannot be handled by __call � ...or provide the functions (here as proxy/ forward) cl ass M yI t er at or W r apper i m pl em ent s I t er at or { I nt er f ace I t er at or { f unct i on __const r uct ( I t er at or $i t ) f unct i on r ewi nd( ) ; { f unct i on val i d( ) ; $t hi s- >i t = $i t ; f unct i on cur r ent ( ) ; } f unct i on __cal l ( $f unc, $ar gs) f unct i on key( ) ; { f unct i on next ( ) ; $cal l ee = ar r ay( $t hi s- >i t , $f unc) ; } i f ( ! i s_cal l abl e( $cal l ee) ) { t hr ow new BadM et hodCal l Except i on( ) ; } r et ur n cal l _user _f unc_ar r ay( $cal l ee, $ar gs) ; } f unct i on r ewi nd( ) { $t hi s- >i t - >r ewi nd( ) ; } f unct i on val i d( ) { r et ur n $t hi s- >i t - >val i d( ) ; } f unct i on cur r ent ( ) { r et ur n $t hi s- >i t - >cur r ent ( ) ; } f unct i on key( ) { r et ur n $t hi s- >i t - >key( ) ; } f unct i on next ( ) { $t hi s- >i t - >next ( ) ; } } Marcus Börger Introduction to Object-oriented programming with PHP 72
Expecting formatted data � Opening a file for reading Run-Time: File might not be accessible or exist $f o = new Spl Fi l eO bj ect ( $f i l e) ; $f o- >set Fl ags( Spl Fi l eO bj ect : : DRO P_NEW LI NE) ; $dat a = ar r ay( ) ; Marcus Börger Introduction to Object-oriented programming with PHP 73
Expecting formatted data � Reading a formatted file line by line Run-Time: File might not be accessible or exist $f o = new Spl Fi l eO bj ect ( $f i l e) ; $f o- >set Fl ags( Spl Fi l eO bj ect : : DRO P_NEW LI NE) ; $dat a = ar r ay( ) ; f or each( $f o as $l ) { i f ( / * * * CHECK DATA * * * / ) { t hr ow new Except i on ( ) ; Run-Time: } data is different for $dat a[ ] = $l ; every execution } � ! pr eg_m at ch( $r egex, $l ) Unexpect Val ueExcept i on � count ( $l =spl i t ( ' , ' , $l ) ) ! = 3 RangeExcept i on � count ( $dat a) > 100 O ver f l owExcept i on Marcus Börger Introduction to Object-oriented programming with PHP 74
Expecting formatted data � Cehcking data after pre-processing Run-Time: Filemight not be accessible or exist $f o = new Spl Fi l eO bj ect ( $f i l e) ; $f o- >set Fl ags( Spl Fi l eO bj ect : : DRO P_NEW LI NE) ; $dat a = ar r ay( ) ; f or each( $f o as $l ) { i f ( ! pr eg_m at ch( ' / \ d, \ d/ ' , $l ) ) { t hr ow new Unexpect edVal ueExcept i on( ) ; Run-Time: } data is different for $dat a[ ] = $l ; every execution } / / Checks af t er t he f i l e was r ead ent i r el y � i f ( count ( $dat a) < 10) t hr ow new Under f l owExcept i on( ) ; � i f ( count ( $dat a) > 99) t hr ow new O ver f l owExcept i on( ) ; � i f ( count ( $dat a) < 10 | | count ( $dat a) > 99) t hr ow new O ut O f BoundsExcept i on( ) ; Marcus Börger Introduction to Object-oriented programming with PHP 75
Expecting formatted data � Processing pre-checked data Run-Time: File might not be accessible or exist $f o = new Spl Fi l eO bj ect ( $f i l e) ; $f o- >set Fl ags( Spl Fi l eO bj ect : : DRO P_NEW LI NE) ; $dat a = ar r ay( ) ; f or each( $f o as $l ) { i f ( ! pr eg_m at ch( ' / \ d, \ d/ ' , $l ) ) { t hr ow new Unexpect edVal ueExcept i on( ) ; Run-Time: } data is different for $dat a[ ] = $l ; every execution } i f ( count ( $dat a) < 10) t hr ow new Under f l owExcept i on( ) ; / / m aybe m or e pr ecessi ng code f or each( $dat a as &$v) { Compile-Time: i f ( count ( $v) == 2) { exception signals t hr ow new Dom ai nExcept i on( ) ; failed precondition } $v = $v[ 0] * $v[ 1] ; } Marcus Börger Introduction to Object-oriented programming with PHP 76
Reflection Marcus Börger Introduction to Object-oriented programming with PHP 77
Reflection API � Can reflect nearly all aspects of your PHP code � Functions � Classes, Methods, Properties � Extensions cl ass Foo { publ i c $pr op; f unct i on Func( $nam e) { echo " Hel l o $nam e" ; } } Ref l ect i onCl ass: : expor t ( ' Foo' ) ; Ref l ect i onO bj ect : : expor t ( new Foo) ; Ref l ect i onM et hod: : expor t ( ' Foo' , ' f unc' ) ; Ref l ect i onPr oper t y: : expor t ( ' Foo' , ' pr op' ) ; Ref l ect i onExt ensi on: : expor t ( ' st andar d' ) ; Marcus Börger Introduction to Object-oriented programming with PHP 78
Dynamic object creation � Reflection allows dynamic object creation cl ass Test { f unct i on __const r uct ( $x, $y = NULL) { $t hi s- >x = $x; $t hi s- >y = $y; } } f unct i on new_obj ect _ar r ay( $cl s, $ar gs = NULL) { r et ur n cal l _user _f unc_ar r ay( ar r ay( new Ref l ect i onCl ass( $cl s) , ' newI nst ance' ) , $ar gs) ; } new_obj ect _ar r ay( ' st dCl ass' ) ; new_obj ect _ar r ay( ' Test ' , ar r ay( 1) ) ; new_obj ect _ar r ay( ' Test ' , ar r ay( 1, 2) ) ; Marcus Börger Introduction to Object-oriented programming with PHP 79
Built-in I nterfaces Marcus Börger Introduction to Object-oriented programming with PHP 80
Built-in Interfaces � PHP 5 contains built-in interfaces that allow you to change the way the engine treats objects. � Ar r ayAccess � I t er at or � I t er at or Aggr egat e � Built-in extension SPL provides more Interfaces and Classes � Ar r ayO bj ect , Ar r ayI t er at or � Fi l t er I t er at or � Recur si veI t er at or � Use CLI: php - - r e SPL php - - r c Ar r ayAccess Marcus Börger Introduction to Object-oriented programming with PHP 81
ArrayAccess � Allows for creating objects that can be transparently accessed by array syntax. � When combined with the iterator interface, it allows for creating ‘arrays with special properties’. i nt er f ace Ar r ayAccess { / / @ r et ur n whet her $of f set i s val i d ( t r ue/ f al se) f unct i on of f set Exi st s( $of f set ) ; / / @ r et ur n t he val ue associ at ed wi t h $of f set f unct i on of f set G et ( $of f set ) ; / / associ at e $val ue wi t h $of f set ( st or e t he dat a) f unct i on of f set Set ( $of f set , $val ue) ; / / unset t he dat a associ at ed wi t h $of f set f unct i on of f set Unset ( $of f set ) ; } Marcus Börger Introduction to Object-oriented programming with PHP 82
ArrayAccess � ArrayAccess does not allow references (the following is an error) cl ass M yAr r ay ext ends Ar r ayAccess { f unct i on &of f set G et ( $of f set ) { / * . . . * / } f unct i on of f set Set ( $of f set , &$val ue) { / * . . . * / } f unct i on of f set Exi st s( $of f set ) { / * . . . * / } f unct i on of f set Unset ( $of f set ) { / * . . . * / } } Marcus Börger Introduction to Object-oriented programming with PHP 83
ArrayAccess Example � We want to create variables which can be shared between processes. � We will set up interception so that access attempts on the variable are actually performed through a DBM file. Marcus Börger Introduction to Object-oriented programming with PHP 84
Binding Access to a DBM <?php cl ass DbaReader i m pl em ent s Ar r ayAccess { pr ot ect ed $db = NULL; f unct i on __const r uct ( $f i l e, $handl er ) { i f ( ! $t hi s- >db = dba_open( $f i l e, ' cd' , $handl er ) ) t hr ow new except i on( ' Coul d not open f i l e ' . $f i l e) ; } f unct i on __dest r uct ( ) { dba_cl ose( $t hi s- >db) ; } f unct i on of f set Exi st s( $of f set ) { r et ur n dba_exi st s( $of f set , $t hi s- >db) ; } f unct i on of f set G et ( $of f set ) { r et ur n dba_f et ch( $of f set , $t hi s- >db) ; } f unct i on of f set Set ( $of f set , $val ue) { r et ur n dba_r epl ace( $of f set , $val ue, $t hi s- >db) ; } f unct i on of f set Unset ( $of f set ) { r et ur n dba_del et e( $of f set , $t hi s- >db) ; } } ?> Marcus Börger Introduction to Object-oriented programming with PHP 85
A Trivial Example <?php i f ( ! cl ass_exi st s( ' DbaReader ' , f al se) ) { r equi r e_once ‘ dbadeader . i nc’ ; } $_SHARED = new DbaReader ( ' / t m p/ . count er ' , ' f l at f i l e' ) ; $_SHARED[ ' count er ' ] += 1; pr i nt f ( " PI D: % d\ nCO UNTER: % d\ n" , get m ypi d( ) , $_SHARED[ ' count er ' ] ) ; ?> Marcus Börger Introduction to Object-oriented programming with PHP 86
Iterators � Normal objects behave like arrays when used with the foreach construct � Specialized Iterator objects can be iterated differently <?php cl ass O bj ect { publ i c $pr op1 = " Hel l o " ; publ i c $pr op2 = " W or l d\ n" ; } f or each( new O bj ect as $pr op) { echo $pr op; } ?> Marcus Börger Introduction to Object-oriented programming with PHP 87
What are Iterators � Iterators are a concept to iterate anything that contains other things. � Iterators allow to encapsulate algorithms Marcus Börger Introduction to Object-oriented programming with PHP 88
What are Iterators � Iterators are a concept to iterate anything that contains other things. Examples: � Values and Keys in an array Ar r ayO bj ect , Ar r ayI t er at or � Text lines in a file Spl Fi l eO bj ect � Files in a directory [ Recur si ve] Di r ect or yI t er at or � XML Elements or Attributes ext: SimpleXML, DOM � Database query results ext: PDO, SQLite, MySQLi � Dates in a calendar range PECL/ date (?) � Bits in an image ? � Iterators allow to encapsulate algorithms Marcus Börger Introduction to Object-oriented programming with PHP 89
What are Iterators � Iterators are a concept to iterate anything that contains other things. Examples: � Values and Keys in an array Ar r ayO bj ect , Ar r ayI t er at or � Text lines in a file Spl Fi l eO bj ect � Files in a directory [ Recur si ve] Di r ect or yI t er at or � XML Elements or Attributes ext: SimpleXML, DOM � Database query results ext: PDO, SQLite, MySQLi � Dates in a calendar range PECL/ date (?) � Bits in an image ? � Iterators allow to encapsulate algorithms � Classes and Interfaces provided by SPL: AppendI t er at or , Cachi ngI t er at or , Li m i t I t er at or , Fi l t er I t er at or , Em pt yI t er at or , I nf i ni t eI t er at or , NoRewi ndI t er at or , O ut er I t er at or , Par ent I t er at or , Recur si veI t er at or , Recur si veI t er at or I t er at or , Seekabl eI t er at or , Spl Fi l eO bj ect , . . . Marcus Börger Introduction to Object-oriented programming with PHP 90
Array vs. Iterator � An array in PHP $ar = ar r ay( ) � can be rewound: r eset ( $ar ) � is valid unless it's key is NULL: ! i s_nul l ( key( $ar ) ) � have current values: cur r ent ( $ar ) � have keys: key( $ar ) � can be forwarded: next ( $ar ) � Something that is traversable $i t = new I t er at or ; � m ay know how to be rewound: $i t - >r ewi nd( ) ( does not r et ur n t he el em ent ) � should know if there is a value: $i t - >val i d( ) � m ay have a current value: $i t - >cur r ent ( ) � m ay have a key: $i t - >key( ) ( m ay r et ur n NULL at any t i m e) � can forward to its next element: $i t - >next () Marcus Börger Introduction to Object-oriented programming with PHP 91
The big difference � Arrays � require memory for all elements � allow to access any element directly � I terators � only know one element at a time � only require memory for the current element � forward access only � Access done by method calls � Containers � require memory for all elements � allow to access any element directly � can create external Iterators or are internal Iterators Marcus Börger Introduction to Object-oriented programming with PHP 92
The basic concepts � Iterators can be internal or external also referred to as active or passive � An internal iterator modifies the object itself � An external iterator points to another object without modifying it � PHP always uses external iterators at engine-level � Iterators may iterate over other iterators Marcus Börger Introduction to Object-oriented programming with PHP 93
PHP Iterators � Anything that can be iterated implements Tr aver sabl e Tr aver sabl e � Objects implementing Tr aver sabl e Tr aver sabl e can be used in f or each f or each � User classes cannot implement Tr aver sabl e Tr aver sabl e � I t er at or Aggr egat e I t er at or Aggr egat e is for objects that use external iterators � I t er at or I t er at or is for internal traversal or external iterators Traversable Iterator IteratorAggregate + rewind () : void + valid () : boolean + current () : mixed + getIterator () : Iterator + key () : mixed + next () : void Marcus Börger Introduction to Object-oriented programming with PHP 94
Implementing Iterators Traversable Iterator IteratorAggregate + rewind () : void + valid () : boolean + getIterator () : Iterator + current () : mixed + key () : mixed + next () : void IteratorImpl AggregateImpl + <<Implement>> rewind () : void + <<Implement>> valid () : boolean + <<Implement>> getIterator () : Iterator + <<Implement>> current () : mixed + <<Implement>> key () : mixed + <<Implement>> next () : void Marcus Börger Introduction to Object-oriented programming with PHP 95
How Iterators work � Iterators can be used manually � Iterators can be used implicitly with foreach <?php $o = new Ar r ayI t er at or ( ar r ay( 1, 2, 3) ) ; $o- >r ewi nd( ) ; whi l e ( $o- >val i d( ) ) { $key = $o- >key( ) ; $val = $o- >cur r ent ( ) ; / / som e code $o- >next ( ) ; } ?> <?php $o = new Ar r ayI t er at or ( ar r ay( 1, 2, 3) ) ; f or each( $o as $key => $val ) { / / som e code } ?> Marcus Börger Introduction to Object-oriented programming with PHP 96
How Iterators work � Internal Iterators � User Iterators < ?php interface Iterator { function rewind(); function valid(); function current(); function key(); function next(); } ?> < ?php $it = get_resource(); for ($it-> rewind(); $it-> valid(); $it-> next()) { $value = $it-> current(); $key = $it-> key(); } ?> Marcus Börger Introduction to Object-oriented programming with PHP 97
How Iterators work � Internal Iterators � User Iterators < ?php interface Iterator { function rewind(); function valid(); < ?php function current(); $it = get_resource(); function key(); foreach($it as $key= > $val) { function next(); / / access data } } ?> ?> Marcus Börger Introduction to Object-oriented programming with PHP 98
How Iterators work � Internal Iterators � User Iterators < ?php class FilterIterator implements Iterator { < ?php function __construct(Iterator $input)... interface Iterator { function rewind()... function rewind(); function accept()... function valid(); function valid()... function current(); function current()... function key(); function key()... function next(); function next()... } } ?> ?> < ?php $it = get_resource(); foreach(new Filter($it, $filter_param) as $key= > $val) { / / access filtered data only } ?> Marcus Börger Introduction to Object-oriented programming with PHP 99
Debug Session <?php <?php PHP 5.1 cl ass Ar r ayI t er at or { $a = ar r ay( 1, 2, 3) ; pr ot ect ed $ar ; $o = new Ar r ayI t er at or ( $a) ; f unct i on __const r uct ( Ar r ay $ar ) { f or each( $o as $key => $val ) { $t hi s- >ar = $ar ; echo " $key => $va\ n" ; } } f unct i on r ewi nd( ) { ?> r ewi nd( $t hi s- >ar ) ; } f ucnt i on val i d( ) { 0 => 1 r et ur n ! i s_nul l ( key( $t hi s- >ar ) ) ; 1 => 2 } 2 => 3 f unct i on key( ) { r et ur n key( $t hi s- >ar ) ; } f ucnt i on cur r ent ( ) { r et ur n cur r ent ( $t hi s- >ar ) ; } f unct i on next ( ) { next ( $t hi s- >ar ) ; } } ?> Marcus Börger Introduction to Object-oriented programming with PHP 100
Recommend
More recommend
