diff options
Diffstat (limited to 'Zend/RFCs/001.txt')
| -rw-r--r-- | Zend/RFCs/001.txt | 136 |
1 files changed, 0 insertions, 136 deletions
diff --git a/Zend/RFCs/001.txt b/Zend/RFCs/001.txt deleted file mode 100644 index bf1d847b97..0000000000 --- a/Zend/RFCs/001.txt +++ /dev/null @@ -1,136 +0,0 @@ -Revamped object model using object handles -=========================================== - -Background ----------- - -In the Zend Engine 1.0 (and its predecessor the PHP 3 scripting -engine) the object model's design is that instantiated objects are -language values. This means that when programmers are performing -operations, such variable assignment and passing parameters to -functions, objects are handled very similarly to the way other -primitive types are handled such as integers and strings. -Semantically this means that the whole object is being copied. The -approach Java takes is different where one refers to objects by handle -and not by value (one can think of a handle as an objects' ID). - -Need ----- - -Unfortunately, the approach taken up to now has severely limited the -Zend Engine's object oriented model, both feature and simplicity -wise. One of the main problems with the former approach is that object -instantiation and duplication is very hard to control, a problem which -can not only lead to inefficient development but also often to strange -run-time behavior. Changing the object model to a handle oriented -model will allow the addressing of many needs such as destructors, -de-referencing method return values, tight control of object -duplication and more. - -Overview --------- - -The proposed object model is very much influenced by the Java -model. In general, when you create a new object you will be getting a -handle to the object instead of the object itself. When this handle is -sent to functions, assigned and copied it is only the handle which is -copied/sent/assigned. The object itself is never copied nor -duplicated. This results in all handles of this object to always point -at the same object making it a very consistent solution and saving -unnecessary duplication and confusing behavior. - -Functionality -------------- - -After this change the basic use of objects will be almost identical to -previous versions of the scripting engine. However, you won't bump -into awkward and confusing copying & destructing of objects. In order -to create and use a new object instance you will do the following: -$object = new MyClass(); $object->method(); - -The previous code will assign $object the handle of a new instance of -the class MyClass and call one of its methods. - - -Consider the following code: - -1 class MyClass -2 { -3 function setMember($value) -4 { -5 $this->member = $value; -6 } -7 -8 function getMember() -9 { -10 return $this->member; -11 } -12 } -13 -14 function foo($obj) -15 { -16 $obj->setMember("foo"); -17 } -18 -19 $object = new MyClass(); -20 $object->setMember("bar"); -21 foo($object); -22 print $object->getMember(); - -Without the new Java-like handles, at line 20 the objects' data member -member is set to the string value of "bar". Because of the internal -representation of objects in the Zend Engine 1.0, the object is marked -as a reference, and when it is sent by value to the function foo, it -is duplicated (!). Therefore, the call to foo() on line 21 will -result in the $obj->setMember("foo") call being called on a duplicate -of $object. Line 22 will then result in "bar" being printed. - -This is how the scripting engine has worked until today. Most -developers are probably unaware of the fact that they aren't always -talking to the same object but often duplicates; others may have -realized this can usually be solved by always passing objects by -reference (unless a replica is actually desired, which is uncommon). - -The new object model will allow for a much more intuitive -implementation of the code. On line 21, the object's handle (ID) is -passed to foo() by value. Inside foo(), the object is fetched -according to this handle and, therefore, the setMember() method is -called on the originally instantiated object and not a copy. Line 22 -will therefore result in "foo" being printed. This approach gives -developers tighter control of when objects are created and duplicated. -An additional not-as-important benefit is that the object handle will -be passed to foo() by value, which most probably will also save -unnecessary duplication of the value containing the ID itself and thus -additionally improving run-time performance. - -This was just a simple description of why the new object model solves -awkward behavior and makes object handling much easier, intuitive and -efficient. The importance of this change goes far beyond what is -mentioned in this section as you will see in further sections which -describe new features with a majority of them being based on this -change. - -Compatibility Notes --------------------- - -Many PHP programmers aren't even aware of the copying quirks of the -current object model and, therefore, there is a relatively good chance -that the amount of PHP applications that will work out of the box or -after a very small amount of modifications would be high. - -To simplify migration, version 2.0 will support an optional -'auto-clone' feature, which will perform a cloning of the object -whenever it would have been copied in version 1.0. Optionally, it -will also be possible to request that the engine will emit an E_NOTICE -message whenever such an automatic clone occurs, in order to allow -developers to gradually migrate to the version 2.0-style behavior -(without automatic clones). - -Dependencies ------------- - -The new object model is not dependent on other features. Many of the -other Zend Engine 2.0 features, such as the $foo->bar()->barbara() -syntax, destructors and others completely rely on this new object -model. - |