RE: [PHP-DEV] RE: PHP 4.0 Bug #6193 Updated: new object makes a shallow copy

Stanislav , >>> Sorry, you misunderstand what references are in PHP. The are not like >>> pointers in C. Not even close. Sorry - I don't. I designed and partially implemented very large projects. using reference counted C++ classes (C++ w/o pointers). I knew very well Java, Perl, ... A compared PHP4.0 with our referere counted classes - and it's close. There are just 4 design and implementation bugs. The PHP was very close to a clean reference counted design. Better than Java (no garbage collection), better than C++ (no counters anymore). For me the best compromise for circular references in a reference counted environment is to leave it to the class designer to unset the class. PHP fails, because: - The double &'s are crazy and a very bad compiler design. This is not a bug - it's just a very bad design. Implementers give there problem back to the user, that's all. - just never, never do implicit shallow copies (C++: copy constructor, Java: special function, ...) - member(&x) { $x= &$this; } is broken. $x= &give_me_your_this(); // works member_function() { $x= &this; }; // fails - references-to-references does not work: $x= &$y->member(); $z= $x->member(); // works $z= $y->member()->member(); // fails - a automatically called destructor would leave the cleanup to the class designer. So the class user need to worry. These 4 points are simple - and very close to the overall PHP design. But, missing those 4 makes PHP very bad for using classes. Today, the PHP class behaviour is good for fun, but ... >>> Please, read some theory on reference counting systems. Every paper on >>> this topic states clearly that the main and almost unavoidable problem of >>> pure reference counting system is isolated circular references. I DID many times in my live!!!! Please read yourself again - they discuss compilers handling this case automatically. Yes this is a bad problem, garbage collections ...... BUT, look at my example (the 100.000.000 loop). I as a class designer can destruct the circular reference easily. But, it's now the responsibility of the class designer not of the compiler. It's like mathematical equations: If you ignore the assumptions, you will never anderstand the equations. OK, my conclusion out of this discussion: we will give up PHP for everything more than 10 lines. JSP seems very clear better suited for complex design. (too bad, I'm not a friend of Sun, I dislike garbage collections, manuals 10 feet long, but I like the working, not broken object model!). Please understand, we would have never used PHP3 because of the oo limitations. After reading the planned changed it looked great. But those 5 issues from above are just too much - plus too many, who should first read books about oo and reference counting before impementing a compiler with oo structures. Sorry. Greetings Heinz -----Original Message----- From: Stanislav Malyshev [mailto:stas@zend.com] Sent: Freitag, 18. August 2000 21:03 To: Heinz Doerr Cc: 'Bug Database' Subject: Re: [PHP-DEV] RE: PHP 4.0 Bug #6193 Updated: new object makes a shallow copy HD>> The change: HD>> 1.) The new constructor always returns references or alternatelly HD>> we would need a syntax like &new HD>> 2.) The assignment operator handles references as references not HD>> as the value of the reference. >>> Sorry, you misunderstand what references are in PHP. The are not like >>> pointers in C. Not even close. -- Stanislav Malyshev stas@zend.com +972-3-6139665 ext.106