Annotation of embedaddon/php/Zend/RFCs/002.txt, revision 1.1.1.1
1.1 misho 1: Title: Zend 2.0 Namespaces
2: Version: $Revision: 148341 $
3: Status: declined
4: Maintainer: Stig S. Bakken <ssb@php.net>
5: Created: 2001-09-08
6: Modified: 2001-09-08
7:
8:
9: 1. Background/Need
10: ==================
11:
12: PHP and Zend 1.0 have come to a point where a lot of reusable code is
13: being written; from simple functions and classes to entire application
14: frameworks. It is becoming increasingly difficult to avoid symbol
15: name collisions with the current scoping methods.
16:
17: The symbol scopes available in Zend 1.0 are the global scope, the
18: class scope and the function scope. All scopes but classes may
19: contain variables, only the class and global scopes may contain
20: functions, while only the global scope may contain constants and
21: classes. This means that all of Zend 1.0's scoping methods are
22: inherently limited for solving symbol name collision problems.
23:
24:
25: 2. Overview
26: ===========
27:
28: Namespaces in Zend 2.0 provide a way to manage the symbol collision
29: problem by making it possible to define multiple symbol tables able to
30: contain all types of symbols. Zend will get the notion of a current
31: namespace, defaulting to the current global one. The current name
32: space may be changed on a file-by-file basis. Symbols in other name
33: spaces than the current one may be referenced using a new namespace
34: operator. It will be possible to "import" symbols from one namespace
35: into another.
36:
37:
38: 3. Functionality
39: ================
40:
41: 3.1. Namespace Syntax
42: =====================
43:
44: The namespace operator ":" is used to refer to symbols in other
45: namespaces than the current one:
46:
47: Class: Namespace:class
48: Function: Namespace:function
49: Static method: Namespace:class::method
50: Variable: $Namespace:variable
51: Constant: Namespace:CONSTANT
52: Class variable: $Namespace:class::variable
53:
54: To refer to symbols in the global namespace, symbols are prefixed with
55: only the namespace operator:
56:
57: Class: :class
58: Function: :function
59: Static method: :class::method
60: Variable: $:variable
61: Constant: :CONSTANT
62: Class variable: $:class::variable
63:
64: Note: $:variable will effectively be just another syntax for
65: $GLOBALS['variable'].
66:
67: A namespace may have a name containing a ":", it is always the last
68: ":" character in the symbol qualifier that is the actual namespace
69: operator:
70:
71: Class: Name:Space:class
72: Function: Name:Space:function
73: Static method: Name:Space:class::method
74: Variable: $Name:Space:variable
75: Constant: Name:Space:CONSTANT
76: Class variable: $Name:Space:class::variable
77:
78: (Here, the ":" between "Name" and "Space" is part of the name, it is
79: the one after "Space" that is the namespace operator.)
80:
81:
82: 3.2. Defining Namespaces
83: ========================
84:
85: Individual files may define a namespace that will apply to the entire
86: file. If no "namespace" operator occurs in the file, it will be in
87: the global namespace:
88:
89: 1 namespace HTML;
90: 2
91: 3 class Form {
92: 4 function Form() {
93: 5 // constructor
94: 6 }
95: 7 // ...
96: 8 }
97:
98: Or with the "nested" name syntax:
99:
100: 1 namespace HTML:Form;
101: 2
102: 3 class Image {
103: 4 var $src;
104: 5 function Image($src) {
105: 6 $this->src = $src;
106: 7 }
107: 8 // ...
108: 9 }
109:
110: Code executed within the "HTML" namespace may refer to the Form class
111: as just "Form". Code executed from within other namespaces has to
112: refer to it as "HTML:Form". The "namespace" statement must occur
113: before any other statements in the file.
114:
115: # [ssb 2001-09-08]:
116: # Should it be possible to "add" symbols to a namespace by including a
117: # second file with the same namespace statement?
118:
119:
120: 3.3. Importing Symbols
121: ======================
122:
123: It is possible to import symbols from another namespace into the
124: current one with the "import" statement:
125:
126: import * from HTML; // all symbols
127:
128: import Form from HTML; // single symbols
129:
130: import Form,Table from HTML; // multiple symbols
131:
132: There is a potential for name clashes between symols of different
133: types that have the same qualifier syntax. These are resolved in this
134: order: class, function, constant.
135:
136: Optionally, the symbol type may be explicitly given to import (as
137: "class", "function", "variable" or "constant"):
138:
139: import class Form from HTML;
140:
141: And finally, you may import all symbols of a given type:
142:
143: import constant * from HTML:Table;
144:
145: The namespace with its symbols must already be defined before using
146: "import".
147:
148:
149: 4. Compatibility Notes
150: ======================
151:
152: Old code that does not take advantage of namespaces will run without
153: modifications.
154:
155:
156: 5. Dependencies
157: ===============
158:
159: The class variable syntax depends on this class variables being
160: implemented in the new ZE2 object model.
161:
162:
163: 6. Acknowledgements
164: ===================
165:
166: Andi Gutmans <andi@zend.com> and Zeev Suraski <zeev@zend.com> for
167: initial ZE2 namespaces proposal
168:
169: Dean Hall <php@apt7.com> for the initial symbol qualification syntax
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