Re: [PHP] Beginner Tutorials for using CLASSES in PHP4


""Nathan Nobbe"" <quickshiftin@xxxxxxxxx> wrote in message
news:7dd2dc0b0710030811g43d5f4e8ka0d6c14633794412@xxxxxxxxxxxxxxxxx
keeping data private is how encapsulation in facilitated.

Absolute rubbish. Encapsulation is the act of placing data and the
operations that perform on that data in the same class. The data does not
have to be private at all.

here is a really simple way to violate encapsulation in php4

class BreakMe {
// private
var $iWishIWasPrivate;
}

// later on

$instance = new BreakMe();

$instance->iWishIWasPrivate = 'encapsulation violated';

if the member variable was supposed to be private well we have just
violated
encapsulation.

Encapsulation is NOT data hiding.

further more when you migrate to php5 you will find many
headaches
as you mark the would-be private variable in php4 private in php5.

My code has to run using both PHP 4 and PHP 5, so I don't waste my time
marking any variables as private or protected.

the proper technique is to drive all access to member variables in php4
through member functions.

That is *A* technique, but not the only technique.

the problem that arises is anybody can simply go and violate the
encapsulation
as i have demonstrated w/o any warning.

I repeat, encapsulation has absolutely nothing to do with data hiding.

the only way to discover this is
through reading
the code, which in a large environment is a lengthy time consuming
process.

i never said interfaces needed to be used to facilitate polymorphism. i
just said they supply an additional means of polymorphism,

I do not need an interface to access a method, therefore interfaces are
redundant.

its actually more powerful than inheritance alone because
a class can implement any number of interfaces, not just one parent class.

A class can implement any number of methods, and I do not need interfaces to
access those mehods, so interfaces are redundant.

also, interfaces
dont require that the behavior be carried over, which is one of the
problems
w/ overusing
inheritance; it isnt always the case that behavior should be propagated.

Then don't overuse inheritance.

admittedly your abstract class mechanism is somewhat similar to what the
keyword supplies in
php5, but i beg the question; why clutter up userspace and contrive
techniques that the language
supplies in php5.

Because I originally wrote my code using PHP 4, and the same code has to run
in both PHP 4 and PHP 5.

php4 is outdated; that is the point.

But is is still widely used. There are a lot of hosting companies who have
yet to upgrade to PHP 5, so the need for PHP 4 is still there.

for someone trying to learn oop, i
maintain that doing so using php4
is a waste of time.

That is just your opinion. I beg to differ.

that would be like learning java4 even though java6 is
in use, its just silly.

But if a lot of servers refused to upgrade from java 4 it would be pointless
using code that only worked in java 6..

--
Tony Marston
http://www.tonymarston.net
http://www.radicore.org

-nathan

On 10/3/07, Tony Marston <tony@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:


""Nathan Nobbe"" <quickshiftin@xxxxxxxxx> wrote in message
news:7dd2dc0b0710030636w5dc967f9yfeb9bf768724d43e@xxxxxxxxxxxxxxxxx
there is no way to create an abstract class in php4.

Oh yes there is! I knw, because I have done it! The definition of an
abstrract class is one that cannot be instantiated into an object. It
can,
however, be extended into a subclass, and that subclass can be
instantiated
into an object.

Although in PHP 5 this can be achieved by using the "abstract" keyword in
the class definition, in PHP 4 you can achieve exactly the same result by
defining a method in the abstract class which contains code which forces
an
error, but when redefined in the subclass this code is replaced so that
it
does not cause an error.

The end result is the same, but the mechanism is different.

in an abstract class definition subclasses are forced to implement
those
methods
that have been declared abstract. or they are allowed to declare the
method
as abstract themselves and force their children to provide a concrete
definition.
the only way to achieve this in php4 is to have an essentially empty
definition in a

Not an empty definition, but one that contains code which triggers an
error.

class and through external documentation or communication w/ other
developers,
indicate the function need be overridden to be usable.
communicating externally, something that could be communicated inside
the
language
itself is very delicate, one that would not do well in a scenario with
a
large
number of developers.

interfaces introduce the concept of design-by-contract. they are very
powerful because
they give code another avenue to be polymorphic.

You DO NOT need interfaces to activate a class method.

You DO NOT need interfaces to utilise polymorphism.

inheritance is often
overused because
people dont understand the power of composition and the benefit of
interfaces to facilitate
composition.

Just because SOME people overuse inheritance does not mean that EVERYBODY
overuses inheritance. My class structure is only two levels deep - an
abstract superclass with any number of concrete subclasses underneath it.

for people coming to php4 from languages like java, or even .net;
anything
that
implements proper access control mechanisms, abstract classes and
interfaces; those
people may be able to design systems w/ php4 that are properly
structured.

You do not need access contol mechanisms or interfaces to write properly
structured code.

starting out w/
php4 and trying to learn oop will likely lead individuals into bad
practices
that they cannot foresee
until years down the road, when their systems are growing at a slow
rate
and
they have to
figure out why or somebody who understands oop comes in and explains
where
the problems are.

the most common mistake i encounter with oop php4 is accessing class
member
functions directly.
this is a complete violation of encapsulation and php4 provides no way
to
enforce it.

Absolute rubbish. Keeping data private has nothing to do with
encapsulation.

yes, php4 does provide some of the fundamental oop facilities and its
all
the community had for a while.
the bottom line is the facilities it offers for oop are bare and i see
no
reason to try to understand its
peculiarities and weaknesses when php5 is here and php6 is on the way.

Rubbish. PHP 4's implementation of OO supports classes, objects,
encapsulation, inheritance and polymorphism. That is more than enough for
a
competent programmer. Everything else is eye candy.

--
Tony Marston
http://www.tonymarston.net
http://www.radicore.org

-nathan

On 10/2/07, Tony Marston <tony@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:


""Nathan Nobbe"" <quickshiftin@xxxxxxxxx> wrote in message
news:7dd2dc0b0709292018q6a5aa7d1w1c422628ca00ae7d@xxxxxxxxxxxxxxxxx
although some people believe differently than i; i would argue
trying to learn how to design w/ the classes that php4 provides
is a waste of time.

I disagree. PHP 4 gives you access to classes, encapsulation,
inheriance
and
polymorphism. This is all you need for OO programming. All that extra
crap
in PHP 5 is just window dressing.

most books you will find regarding object oriented
design assume the language has the basic constructs. ppp mainly.
also, there are other important facilities php4 lacks like abstract
classes

You can write abstact classses in PHP 4, it's just that you can't use
the
word "abstract". Interfaces are totally irrelevant as any method can
be
accessed directly through its function definition.

and interfaces, not to mention you have to explicitly assign objects
by
reference in php4. (if you dont want a copy created).
unless you are bound to php4 by work or something
i suggest you start working w/ php5. also, if your looking for some
design
techniques i recommend studying design patterns.

Design patterns are overrated. For building transactions in CRUD
applications you need transaction patterns.

--
Tony Marston
http://www.tonymarston.net
http://www.radicore.org

the heads first book
is a great starting point.
actually if you want a solid reference thats free on the web look at
phpPatterns <http://www.phppatterns.com/docs/start>
the code is mostly php4 i believe.

-nathan


On 9/29/07, Jeff Cohan <jdcohan@xxxxxxxxxxxxx> wrote:

Yes, I know how to Google, and I've been Googling...

But I would appreciate advice about good beginner tutorials using
classes in PHP4 based on your actual experiences. I.e., have some
of
you found tutorials that really unlocked the doors for you?

Ideally, such tutorials would have somewhat realistic examples. (I
already know how to output "Hello, World" using a class, and I tend
to find examples like those unhelpful. Maybe it's just me.)

My main challenge is modularizing yer basic BREAD/CRUD operations
with MySQL databases.

I've made some strides in creating increasingly modular functions
to
present browse lists, edit forms and add forms; to perform
field-level and form-level validations; and to perform inserts,
updates and deletes. My approach is to utilize multidimensional
arrays which define the column names, column labels (for forms),
form control types (input, select, checkbox, etc.) and other
attributes of the form controls. I've got a "library" of validation
routines with error messages that appear on the form under the
culprit form control.

But I think taking the next step to use classes is going to make my
life much easier.

TIA for any guidance you might be able to offer.

Jeff

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