""Nathan Nobbe"" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > 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 <[EMAIL PROTECTED]> wrote: >> >> >> ""Nathan Nobbe"" <[EMAIL PROTECTED]> wrote in message >> news:[EMAIL PROTECTED] >> > 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 <[EMAIL PROTECTED]> 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 >> >> >> >> -- >> >> PHP General Mailing List (http://www.php.net/) >> >> To unsubscribe, visit: http://www.php.net/unsub.php >> >> >> >> >> > >> >> -- >> PHP General Mailing List (http://www.php.net/) >> To unsubscribe, visit: http://www.php.net/unsub.php >> >> > -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
