The PHP Fear and Loathing Guide to Basic Object-Oriented Design

최태리
<?OOps!
The PHP Fear and
Loathing Guide to Basic
Object-Oriented Design
terry chay
tagged
11 February 2009
engineering brownbag

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{introduction
2XtremePeople

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“PhpPatterns is just that—a source of
design patterns for PHP code. Will
wonders never cease? I ran this by a Java
programmer I know that I have drawn
into the PHP world and her comment
was, ‘I’d have never even thought to try
patterns in PHP.’”
—the FuzzyBlog
phppatterns? {

Web Developer Training
PHP to ASP.NET
{

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“ASP.NET applications are based on a robust
Object Oriented Programming (OOP) paradigm
rather than a scripting paradigm…The upside of
ASP.NET’s support of OOP concepts [vs PHP]
means that ASP.NET applications for the most
part run better designed code, have clear
separation of content, logic, and data and thus
are generally easier to support over the long
term.”
—Migrating from PHP to ASP.NET
dotFUD {

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“Although being a young fellow myself, I
have to hold my hand up and say I was
educated in an era before design patterns
were even invented. Yes it’s true, such a
time did exist. In my day, it was called
‘Data Structures’.”
—Alan Williamson, Editor-in-Chief
November 2002
datastructures? {

離
12守
破
shuhold
chinese character “house”
and “law”
to abide by; to defend
the o-o bigot
7 habits: dependence
{

離
13守
破
habreak
chinese character “stone”
+ phonetic
to break
the grumpy old
programmer
7 habits: independence
{

離
14守
破
rileave
chinese character “bird” +
phonetic
to leave; to depart
the middle way
7 habits: interdependence
{

16
myquiz
1:<?php
2:$tests[1] = new stdClass();
4:
5:foreach ($tests as $obj) {
6: $obj->foo = 'bar';
7:}
8:
9:print_r($tests);
10:?>
1.
2.
3.
tychay$ php test.php
Array
(
[1] => stdClass Object
(
)
(
)
)
{
1. construct some generic
PHP objects
2.interate over objects and
assign them a value
3.dump the array of objects
what do you think the
output of this is and why?
UNEXPECTED!

1:<?php
4:
5:foreach ($tests as $obj) {
6: $obj->foo = 'bar';
7:}
8:
9:print_r($tests);
10:?>
17
myquiz
remember that PHP4,
objects are like everything
else, so you need the &!
Otherwise it will use a
copy of the object.
{

1:<?php
2:$tests[1] =& new stdClass();
3:$tests[2] =& new stdClass();
4:
5:foreach ($tests as $count=>$obj) {
6: $tests[$count]->foo = 'bar';
7:}
8:
9:print_r($tests);
10:?>
18
myquiz
tychay$ php answer1.php
Array
(
(
[foo] => bar
)
(
[foo] => bar
)
)
now we’ve ﬁxed the
problem!
{

19
byreference
{
remember this is true also
when:
prints empty object!
1:<?php
2:class testClass
3:{
4: function addObject(&$object)
5: {
6: $this->object = $object;
7: }
8:}
9:$testObject =& new testClass();
10:
11:function addBar($object)
12:{
13: $object->bar = 'this is set also';
14:}
15:addBar($testObject);
16:
17:function getSameObject()
18:{
19: global $testObject;
20: return $testObject;
21:}
22:$returnObject = getSameObject();
23:$returnObject->same = 'this should be in object';
24:
25:class testRefClass
26:{
27: function testRefClass($objFromHell)
28: {
29: $objFromHell->something = 'something here';
30: $objFromHell->addObject($this);
31: }
32:}
33:$tempObject = new testRefClass($testObject);
34:print_r($testObject);
1. passing parameters
3. constructor
2. functions that return
objects

20
{1:<?php
2:class testClass
3:{
4: function addObject(&$object)
5: {
6: $this->object = $object;
7: }
8:}
9:$testObject =& new testClass();
10:
11:function addBar(&$object)
12:{
13: $object->bar = 'this is set also';
14:}
15:addBar($testObject);
16:
17:function &getSameObject()
18:{
19: global $testObject;
20: return $testObject;
21:}
22:$returnObject =& getSameObject();
23:$returnObject->same = 'this should be in object';
24:
25:class testRefClass
26:{
27: function testRefClass(&$objFromHell)
28: {
29: $objFromHell->something = 'something here';
30: $objFromHell->addObject($this);
31: }
32:}
33:$tempObject =& new testRefClass($testObject);
34:print_r($testObject);
byreference
remember this is true also
when:
1. passing parameters
3. constructor
2. functions that return
objects
PHP5 ﬁxes this!

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“…the new object model makes object
oriented programming in PHP much
more powerful and intuitive. No longer
will you have to mess with cryptic &
characters to get the job done. No longer
will you have to worry about whether
changes you made to the object inside
the constructor will survive the dreaded
new-operator behavior…
php5 {

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…No longer will you ever have to stay up
until 2:00AM tracking elusive bugs!”
—Zeev Suraski
November 2002
php5 {
Zeev’s2AMbug

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23
staticproperties
no static class variables in PHP.
substitute with
global variables
static function variables (bad idea)
{

24
globalstatic
bind by reference in
constructor (or elsewhere)
1:<?php
2:$GLOBALS['_statics']['testClass']['staticCount'] = 0;
3:class testClass
4:{
5: var $staticCount;
6: function testClass()
7: {
8: $this->staticCount =& $GLOBALS['_statics']
['testClass']['staticCount'];
9: }
10: function increment()
11: {
12: return ++$this->staticCount;
13: }
14:}
15:$test1 =& new testClass();
16:$test2 =& new testClass();
17:$test1->increment();
18:$test2->increment();
19:print_r($test1);
20:print_r($test2);
21:echo testClass::increment();
22:?>
tychay$ php test3.php
testclass Object
(
[staticCount] => 2
)
testclass Object
(
[staticCount] => 2
)
1
watch out though!

25
singleton
one of the simplest
patterns
creates a single instance
of a class (DB
connection)
lazy evaluation
ﬂexible
1:<?php
2:class testSingleton
3:{
4: function &instance()
5: {
6: static $singleton;
7: if (!$singleton) {
8: $singleton =& new testSingleton();
9: }
10: return $singleton;
11: }
12:}
13:$test1 =& testSingleton::instance();
14:$test1->foo = bar;
16:print_r($test2);
17:?>
testsingleton Object
(
)
watch out though!

26
singleton
also note the liberal use
of &
1:<?php
2:$GLOBALS['_statics']['testSingleton']['singleton'] = null;
3:class testSingleton
4:{
5: function &instance()
6: {
7: if (is_null($GLOBALS['_statics']['testSingleton']
['singleton'])) {
8: $GLOBALS['_statics']['testSingleton']['singleton']
=& new testSingleton();
9: }
10: return $GLOBALS['_statics']['testSingleton']
['singleton'];
11: }
12:}
14:$test1->foo = bar;
16:print_r($test2);
17:?>
testsingleton Object
(
[foo] => bar
)

27
latebinding
when a polymorphic call
is resolved at run time
(instead of compile time)
oo-bigots advocate
against (speed, strong
typing)
simple to do in PHP
1:<?php
2:class testLateBinding
3:{
4: function callMeLate()
5: {
6: echo "I was calledn";
7: $this->wasCalled = true;
8: }
9:}
10:$object1 =& new testLateBinding();
11:$object2 =& new testLateBinding();
12:$functionname = 'callMeLate';
13:
14:$object1->{$functionname}();
15:
16:call_user_func(array(&$object2,$functionname));
17:print_r($object2);
18:?>
I was called
I was called
testlatebinding Object
(
[wasCalled] => 1
)
variable-variables
call_user_func()
PHP4.3+
note the &!.
{

29
一
三
二
the why
why do old metaphors
fail?
why use agile processes?
methodology

30
一
三
二
the what
what are the precepts of
class rules
what are the parameters
of package design
what are patterns?
principles

31
一
三
二
the how
how do patterns allow
me to follow principles?
how can patterns work
around a design error?
how do patterns apply to
more than O-O?
patterns

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methodology
一
최채리

一
34
codecomplete
Published 1993
Microsoft “Tome”
Award winning book

35
paradigm
shift
Code Complete is a “wanna
be” Structure of Scientiﬁc
Revolutions
he uses “paradigm shift”
Key premise: key
metaphor of software
should be construction
一

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36
straw men
The metaphor of
construction is so central
to the book, that the
subtitle is: “A Practical
Handbook of Software
Construction.”
Thus it needs to
construct some straw
men of failed metaphors
in order to prove why
we should adopt the
“software as
construction” paradigm.
一

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37
一 1.software
penmanship
“writing code”
causes expensive trial and error
focused on originality > reuse
“plan to throw one away”
“it might have been state-of-the-art
software-engineering practice in 1975”

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39
growing a system “piece by piece”
bad metaphor!
fertilizing a system plan?
thinning the detailed design?
increasing code yields through eﬀective
land managment?
harvesting code?
rotating in a crop of assembler?
Who ever believed this shit?
一

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why Code Complete sucks
software as
construction
一

The #1 reason why
software is not
construction
一
離
守
破

Mythical
Man Month
This is a really famous essay
from 1975. Does the year
sound familiar? Yes, the
Frederick Brooks is the same
engineer treated with derision
in Code Complete’s “Software as
Writing” straw man.
A lot of what he says was
controversial, but one thing
that was never denied was the
man-month was a myth.
What is a mythical man
month?
一

43
man-month
一the premise is that men
and months are
interchangeable.
This means that in order
to reach a deadline I
simply add people to the
project.

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44
man-month
myth
The problem:
Adding people to a late
project makes it later!
ﬁrst consider case where
they’re everything is
partition-able (man-
month).
then add constant time
for training
then add
communication: n(n-1)/2
compare with
unpartitionable (single
man)
최채리

45
where?
man-hour (măn’our')
n.
An industrial unit of production equal
to the work one person can produce
in an hour.
Source: The American Heritage®
Dictionary of the English Language,
Fourth Edition
fromconstruction!
一
programming!=labor

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46
Mythical Man-Month referred to ﬁve
times in Code Complete
Including having the author give an
endorsement on the back cover!
irony
php{con
최채리

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47 최채리
“I’d be astonished if the open-source
community has in total done as many
man-years of computer security code
reviews as we have done in the last two
months”
—Steven Lipner, Director of Security
Assurance, Microsoft (April 8th, 2002)
persistantmyth

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49
“The ﬁnal goal of any engineering
activity is some type of
documentation. When a design eﬀort
is complete, the design documentation
is turned over to the manufacturing
team. If the design documents truly
represent a complete design, the
manufacturing team can proceed to
build the product.”
—Jack Reeves, C++ Journal, 1992
一

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50
“Two Irreparable Mistakes of thre
Software Field: 1. The believe that the
source code is a development product,
not the design for a product.”
—Michael Feathers, ObjectMentor
The other problem with software as
construction:
the “design” phase ﬁnishes with
working source code
it’s based on the illusion that the
source code is the product!
一

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51
How did we buy this illusion?
“It is cheaper and simpler to build the
design and test it than do anything else.
We do not care how many builds we do
—they cost next to nothing…No other
modern industry would tolerate a
rework rate of over 100% in its
manufacturing process”
—Jack Reeves, C++ Journal, 1992
a software “build” means
“manufacturing” phase is cheap.
一

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離
守
破
A software developer is more akin to an
artist than an assembly line worker…
Throwing more people into the design
mix can be counterproductive.
—Jason Burkert
“Software as engineering” accepts the
reality of the mythical man-month!
The source code is the design.
離
一

53
roadmap
一
三
二
now that we’ve talked
discussed the paradigm or
metaphor it is time to apply
that to programming
practice.

54
heavyweight
離
守
破
methodologies like
ISO9001 violate
“software as an
engineering”
by deﬁnition
treat auxiliary
documentation as the
product

55
Note inﬂuence of
construction metaphor
BDUF: Big Design Up
Front
Big Bang Delivery
waterfall
SYSTEM
SPECIFICATION
REQUIREMENTS
ANALYSIS
ARCHITECTURAL
DESIGN
CODING AND
DEBUGGING
DETAILED DESIGN
UNIT TESTING
SYSTEM TESTING
MAINTAINENCE
from Code Complete, p.3
BDUF
Big Bang
一

56
changing requirements
constant release schedule
not life-death
“The reason why dynamic
languages like Perl, Python,
and PHP are so important …
Unlike applications from the
previous paradigm, web
applications are not released
in one to three year cycles.
They are updated every day,
sometimes every hour.”
—Tim O’Reilly, 14 May 2003
websoftware
一

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57
“The biggest mistake in ‘Build one to
throw away’ concept is that it implicitly
assumes the classical sequential or
waterfall model of software
construction.”
—Frederick Brooks, Mythical Man-
Month, 20th Aniv. 1995
moreirony
一

59
XP
離
守
破
ship early and often!
one of many lightweight
methodologies known as
“agile”
I’ll cover three features
of XP. So you get an idea
of what is considered an
“agile” process
一

designbytest
recall the waterfall process.
Look at where the unit
testing is.
recall the “software as
engineering” metaphor: tests
and builds are cheap. Why
aren’t we leveraging it?
We should be testing ﬁrst and
using testing as a design
technique (the hard part of
engineering), not a testing
technique (easy part).
SYSTEM
SPECIFICATION
REQUIREMENTS
ANALYSIS
ARCHITECTURAL
DESIGN
CODING AND
DEBUGGING
DETAILED DESIGN
UNIT TESTING
SYSTEM TESTING
MAINTAINENCE
一

1:<?php
2:class MoneyBagTest extends TestCase {
3:    var $m12CHF;
4:    var $m14CHF;
5:    var $m28USD;
6:    var $mArray1;
7:    var $moneybag1;
8:    var $moneybag2;
9: function MoneyBagTest( $name = "MoneyBagTest" ) {
10: $this->TestCase( $name );
11: }
12:
13: function setUp() {
14: $this->m12CHF = new Money( 12, "CHF" );
15: $this->m14CHF = new Money( 14, "CHF" );
16: }
17: function tearDown() {
18: $this->m12CHF = NULL;
19: $this->m14CHF = NULL;
20: $this->m28USD = NULL;
21: }
22:
23: function testSimpleAdd() {
24: $result = $this->m12CHF->add( $this->m14CHF );
25: $this->assert(new Money(27,"CHF"), $result, "This
should fail" );
26: $this->assertEquals(new Money(27,"CHF"), $result,
"This should fail" );
27: }
28:
29: // insert more tests here: use "test..." for name of
function.
30:}
62
code unit test
ﬁrst
1. Code the Unit Test
First
2. Write minimum code
until test works
3. Refactor (see later)
4. Rerun tests
constructor
a test
一
ﬁxture

keep the bar green to keep the code clean…
31:
32:$test = new MoneyBagTest();
33:$testRunner = new TestRunner();
34:$testRunner->run($test);
35:?>一

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65
“The process of changing a software
system in such a way that does not alter
the external behavior of the code yet
improves the internal structure”
—Martin Fowler, Refactoring, 1999
the changes by themselves are tiny
focus on simplicity (in design) not
simplistic (implementation)
refactorit!
一

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66
do this continuously
purpose of a module of code:
function it performs
allow change
communicate
prevents code rot in large projects
my experience.
refactorit!
一

3.You Aren’t Going to Need
It (YAGNI)
一

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68
Implement the simplest thing that
could possibly work.
Basically, if you need it, you can put it
in later—it does not “save time.”
Set aside your fears about tomorrow
and concentrate on today.
whatisYAGNI?

최태리
69
YAGNIperks
keeps system smaller and easier to
understand (form of refactoring)
more likely to ship out the door if you
focus on needs
allows for system accretion
recall how fast a web iteration vs. Big
Bang

최태리
70
“A project done in Java will cost 5
times as much, take twice as
long, and be harder to maintain
than a project done in a scripting
language such as PHP or Perl,”
—Philip Greenspun
20 September 2003

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71
lack of rigid O-O deﬁnitely a plus!
recall the “Migrating from PHP to
dotNET” document
lack of framework deﬁnitely a plus!
phpYAGNI

72
Well bad pattern for a
loosly typed language
such as PHP!
Iterator Pattern: provide
a way to access the
element of an aggregate
object sequentially
without exposing its
underlying
representation
badpattern
Aggregate
CreateIterator()
ConcreteAggregate
+ CreateIterator()
Iterator
+ First()
+ Next()
+ IsDone()
+ CurrentItem()
ConcreteIterator
return new ConcreteIterator(&$this)

1:<?php
2://A lot of code in here...
3:include(ECLIPSE_ROOT.'ArrayIterator.php');
4:
5:$iterator =& new ArrayIterator(&$arrayToBeIterated);
6:while ($element=$iterator->getCurrent()) {
7: echo $iterator->key().' => '.$element;
8: $iterator->next();
9:}
10:$iterator->reset();
11:
12:?>
iterator# phpdefault
You can vary what is being
iterated over (ignoring
constructor)
YAGNI!
If you must have an
iterator there is SPL in
PHP5!
1:<?php
2:foreach($arrayToBeIterated as $key=>$value) {
3: echo $key.' => '.$value;
4:}
5:?>

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74
pair programming
the planning game/user-stories
code reviews
acceptance tests
on-site customer
other processes: SCRUM, Crystal, etc.
code ownership
XPnotcovered
一

75
roadmap
一
三
二
the metaphor/paradigm for
building software is
engineering
we now know agility: the
lightweight processes that
avoid the waterfall process
離
守
破

76
roadmap
一
三
二
What programming
principles help us program
correctly?

78
roadmap
一
三
二
1. What precepts for class
design?
2. Grouping classes into
packages using what
parameters?
3. What are patterns?

최태리
80
single
responsibility
A class should have only one reason to
change.
Each responsibility is an axis of
change.
more than one responsibility =
coupling
二

81
violation
PEAR is great.
Except…
This is the PEAR Error
constructor. Note that
this method causes the
object to violate SRP!
2:function PEAR_Error($message = 'unknown error', $code =
null,
3: $mode = null, $options = null, $userinfo = null)
4:{
5: if ($mode === null) {
6: $mode = PEAR_ERROR_RETURN;
7: }
8: $this->message = $message;
9: $this->code = $code;
10: $this->mode = $mode;
11: $this->userinfo = $userinfo;
12: if (function_exists("debug_backtrace")) {
13: $this->backtrace = debug_backtrace();
14: }
15: if ($mode & PEAR_ERROR_CALLBACK) {
16: $this->level = E_USER_NOTICE;
17: $this->callback = $options;
18: } else {
19: if ($options === null) {
20: $options = E_USER_NOTICE;
21: }
22: $this->level = $options;
23: $this->callback = null;
24: }
25: if ($this->mode & PEAR_ERROR_PRINT) {
26: if (is_null($options) || is_int($options)) {
27: $format = "%s";
28: } else {
29: $format = $options;
30: }
31: printf($format, $this->getMessage());
32: }
33: if ($this->mode & PEAR_ERROR_TRIGGER) {
34: trigger_error($this->getMessage(), $this->level);
35: }

82
and the violation goes on
callbacks
die
return mode
print
trigger_error
exception
36: if ($this->mode & PEAR_ERROR_DIE) {
37: $msg = $this->getMessage();
38: if (is_null($options) || is_int($options)) {
39: $format = "%s";
40: if (substr($msg, -1) != "n") {
41: $msg .= "n";
42: }
43: } else {
44: $format = $options;
45: }
46: die(sprintf($format, $msg));
47: }
48: if ($this->mode & PEAR_ERROR_CALLBACK) {
49: if (is_string($this->callback) && strlen($this-
>callback)) {
50: call_user_func($this->callback, $this);
51: } elseif (is_array($this->callback) &&
52: sizeof($this->callback) == 2 &&
53: is_object($this->callback[0]) &&
54: is_string($this->callback[1]) &&
55: strlen($this->callback[1])) {
56: @call_user_func($this->callback, $this);
57: }
58: }
59: if (PEAR_ZE2 && $this->mode &
PEAR_ERROR_EXCEPTION) {
60: eval('throw $this;');
61: }
62:}
63:?>

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83
Liskov substitution
Subtypes must be substitutable for
their base types.
not an “is-a” relationship
validation of LSP occurs in the client!
(Design By Contract).
二

최태리
84
Design By Contract
validates Liskov
Substituion. What
validates Design by
contract?
Unit Tests! Remember
them? They determine
deﬁne it.
In fact, PEAR PHPUnit
can document a Design
By Contract by reading
the unit test (aka
TestDox).
1:<?php
2:require_once 'PHPUnit/Framework/TestCase.php';
3:
4:class FooTest extends PHPUnit_Framework_TestCase
5:{
6: public function testIsASingleton() {}
7: public function
testAReallyLongNameIsAGoodThing() {}
8:}
9:?>
Foo
- Is a singleton
- A really long name is a good thing

I violate LSP
Look at how naïve this
diagram is. It’s the most
obvious one but focuses on
the physical objects instead of
their behaviors.
The objects are deﬁned in
terms of the clients. Think
about an image coming back
from the camera, or trying to
set a dimmer to a light switch
that turns on or oﬀ only.
Unfortunately I had to live
with it for reasons later.
Common
CameraSwitchable
Sensor
HVAC

최태리
86
otherprecepts
Open-Closed Principle
Dependency-Inversion Principle
Interface Segregation Principle
二

최태리
88
“A few days ago, I was at Microsoft, and
they held an amazing conference…After
this conference, I was kinda depressed
about the future of PHP and Apache…
The ASP.NET stuﬀ is just perfect. Fast,
Secure and Robust. ASP.NET
technology is better than PHP
technology.”
—Sterling Hughes
5 June 2003
二

최태리
Common language Runtime
access to COM+
server ui controls
“code behind” (.cs)
server-side object model
event-driven handlers
automatic page state (ViewState)
built-in Validation object
try-catch
二

최태리
built-in authentication (Web.conﬁg)
built-in database abstraction (ADO.NET) +
connection pooling + data binding
built-in MSXML: DOM, XSLT, SAX + Web
Services
auto targeting of HTML
IDE (Visual Studio .NET)
built-in output caching
I see what Sterling is saying!
However…
二

최태리
Common Language Runtime 2nd class, compiling cache, Pint (Parrot)
access to COM+ access to COM, Java, C/C++ extensions,
mono, command line
server ui controls,“ViewState”- saving
form state
PEAR::HTML_* (Form, Menu, Page…) +
others + BYO
“code behind” smarty, fasttemplate, flexy, it, phplib, +
others, BYO
server-side object model session, __sleep(), __wakeup(), SRM
event driven handlers bad idea, fusebox + zillions of others,
s9y, BYO
output-caching zend accelerator, Cache, Cache_Lite,
free energy, BYO
validation object PEAR::Validate + zillions of others
try-catch in PHP5. no substitute for proper error
handling
“Web.config”- authentication auth, LiveUser, + others
ADO.Net- database abstraction db specific, dbx, PEAR DB, MDB,
ADODB
connection pooling, data-binding pconnect, SRM, only nice on client-side
MSXML expat, DOM, SimpleXML, XMLtree etc.,
2 SOAP, 5 XMLRPC
VisualStudio- IDE Komodo, Zend+ others, text editors

최태리
92
離
守
破
All of them (or equivalent) can be done
in PHP .
I have a choice on a solution—Zend’s
solution doesn’t bankrupt someone
else’s (or me!)
Most solutions are open source so I
don’t have be tied to someone else’s
release-upgrade cycle.
ASP.NET’s large framework violates
YAGNI—encourages o-o bigotry and
bad design.
二

최태리
93
Comparing PHP to
ASP.NET is like
comparing the Linux
kernel to the Windows
Platform.
GNU/Linux is the kernel
+ toolchain. That
toolchain is based on a
lot of small interacting
programs that can be
chained to create
complex behavior.
Windows does the
complicated approach.
we say Unix
has…
二

최태리
95
Frameworks vs.
Libraries
A good package is highly cohesive but
weakly coupled. This creates high
reusability.
Remember the J2EE taking 5x as long
to build? This is why. Too much
framework. When you use one part of
a package, you reuse them all.
This is why PEAR succeeds…
二

최태리
Some of these frameworks are great, but the
best are reused entirely (i.e. shrink-wrapped).
and Frameworks fail
Ariadne, Binary Cloud, Back-End, bBlog,
COWeb, Eocene, ezPublish, FastFrame,
FUDforum, ISMO, Komplete, LogiCreate
Application Server, Mambo, MetaL, Midgard,
more.groupware, NetUse, Nucleus,
phpGroupWare, Phrame, PostNuke,
PHPortal, phpWebSite, Rodin, SiteManager,
serendipity, STPHPLib, tikiwiki, TUTOS,
WordPress, XOOPS…
二

최태리
99
this covers acyclic
dependency
the more you
depend on a
package the more
stable it must be
(think client-
centric)
recall my devices
diagram…
Common
CameraSwitchable
Sensor
HVAC
二

최태리
100
Caveat: I’m going to use
that bad “construction”
analogy…
The Leaning Tower of
Pisa was built on a
shifting foundation. It’s
been leaning since
before it was ﬁnished.
Sounds like the what
happens when you you
try to extend someone
else’s framework.
二

최태리
101
This is a mapping of the
PEAR XML package
dependencies.
Notice how weakly
coupled they are.
Notice the packages
which are depended on.
What happens if the
API is changed.
What if you depend on
them? Better have your
Unit Tests!
XML_ParserXML_Util
XML_Beautifier
XML_CSSML
XML_Tree
XML_DTD
XML_fo2pdf
XML_HTMLSax
XML_image2sv
g
XML_NITF
XML_RSS
XML_SaxFilters
XML_Serializer
XML_sql2xml
XML_Statistics
XML_RDDL
二

102
roadmap
一
三
二
we now know the precepts
by which classes are made
and the parameters by whic
they are packaged into
classes…
離
守
破

103
roadmap
一
三
二
Before we go discuss
patterns it helps to deﬁne
what a pattern is!
If we skip this then we run
the danger of becoming a o-
o bigot or a grumpy old
programmer!
離
守
破

최태리
105
Patterns come from a book on
architecture:
“Each pattern describes a problem
which occurs over and over again in our
environment and then describes the
core of the solution to that problem, in
such a way that you can use this solution
a million times over, without ever doing
it the same way twice.”
—Christopher Alexander, The Timeless
Way of Building, 1979
二

최태리
106
I don’t know architecture.
It makes me think of the software
construction metaphor
Let’s ﬁnd some patterns closer to us…
Web Design!
whatever!

cookie
crumbs
solve deeply
hierarchical
navigation

tabs
solve lateral
navigation along a
few high level
elements

tabs
can use a million
times over, without
ever doing it the
same way twice

최태리
110
二deﬁnedbycontext
Let’s not be an o-o snob.
“tabs” and “cookie crumbs” are both
navigational patterns. Which one is
best to use is deﬁned by context.

patterns are designed to
be linked together
二

최태리
?baddesign
tale of the keyfob
三

115
mybane
Recall my poor design choice.
Now realize that a KeyFob has
four buttons. Each one is a
sensor.
Since I implemented the low
level stuff blindly and this
error occurred on the
presentation tier, the user sees
one keyfob as four devices.
One for each button!
Common
CameraSwitchable
Sensor
HVAC
三

최태리
How to make four
devices appear as one
?
三

최태리
!a pattern a day keeps the
pink slip away
composite
pattern
三

최태리
118
Common
Aggregate
A composite pattern
adds a subclass that
contains 1 or more
elements of the base
class.
Thus it appears to
clients as a single object,
even though it contains
more than one and have
to handle the objects
behind the scenes.
Common
CameraSwitchable
Sensor
HVAC
三

최태리
?phpdoc
decoupled messaging
三

121
phpDocu
phpDocumentor is a PEAR
librar y/application that
tokenizes and parses your
PHP code for JavaDoc style
comments and uses them to
build hyperlinked API docs.
The problem is the parsers
(preg, tokenizer, c-based) and
the renderers (various HTML,
peardoc, XML, PDF) both
will need to vary in the PHP5
version.
The event messaging that
occurs can get quite complex.
三

최태리
How to make a more
robust messaging system
?
三

최태리
!allow one object to notify
many (run-time conﬁg)
observer
pattern
三

최태리
124
An observer registers
with the subject for
notiﬁcation using the
attach() method passing
itself.
The subject notiﬁes all
observers by calling its
notify() which iterates
over all observers and
calls its update() method
You can pass $this to
update() to allow
observer to use subject.
Subject
+ attach(&$observer)
+ detatch(&$observer)
# notify()
Observer
+ update()
ConcreteObserver
+ update()
ConcreteSubject
0..1*
三

최태리
?templates
working friendly with
designers
三

126
shutemplate
dotNet’s serverui
controls and auto page
state are great
but they’re template
systems
however PHP IDE !=
Visual Studio
離
守
破
三

127
1:<html>
2:<head>
3: <title>Example ASP.NET template</title>
4:</head>
5:<body>
6:<script language="VB" runat="server">
7:Sub Page_Load(sender As Object, e As EventArgs)
8: TheDate.Text = DateTime.Now
9:End Sub
10:</script>
11: <p>The current date is: <asp:Label id="TheDate"
runat="server" />.</p>
12:</body>
13:</html>
三
shu
how does this render in
an editor?
how does it separate
model-view-controller?
does MVC really matter
anyway?…

최태리
128
“With Web applications, nearly all the
engineering happens in the SQL
database and the interaction design,
which is embedded in the page ﬂow
links. None of the extra power of Java is
useful…”
—Philip Greenspun
2003 September 20
三

129
hatemplate
PHP is itself a
templating language.
if all web developers are
PHP programmers this
makes the most sense
however
離
守
破
三

1:<html>
2:<head>
3: <title>Example ASP.NET template</title>
4:</head>
5:<body>
6:<script language="VB" runat="server">
7:Sub Page_Load(sender As Object, e As EventArgs)
8: TheDate.Text = DateTime.Now
9:End Sub
10:</script>
11: <p>The current date is: <asp:Label id="TheDate"
runat="server" />.</p>
12:</body>
13:</html>
1:<html>
2:<head>
3: <title>Example simple PHP version</title>
4:</head>
5:<body>
6: <p>The current date is: <?php echo date('l, F dS, y');
?>.</p>
7:</body>
8:</html>
三
shu ha
much smaller and easier to read!
how does a web designer deal with it?

최태리
!doing templates without
o-o
freeenergy
三

132
ritemplate
1. check for compiled
version.
2. if compiled then
include compiled
version
3. if not compiled then
call routine to compile
template
4. use XML!
離
守
破
三

133
1:<?php
2:tc::import('tips');
3:tc::import('tc.error');
4:
5:$template =& new tips();
6:$template->assign('date',date('l, F dS, y'));
7:$template->output('tipsexample.html');
8:?>Separate templates =
separate ﬁles
leverages shu
This is a smarttemplate
like system
leverages ha of php
use XML so the web
developer can work with
1:<tips:template>
2:<html>
3:<head>
4: <title>Example PHP template</title>
5:</head>
6:<body>
7: <p>The current date is: <tips:variable
name="date">Wednesday, October 21st, 2003</
tips:variable>.</p>
8:</body>
9:</html>
10:</tips:template>
三

최태리
?>questions
AndAnswers
三
http://homepage.mac.com/tychay/talks/oops

The PHP Fear and Loathing Guide to Basic Object-Oriented Design

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