Annotation of embedaddon/php/Zend/OBJECTS2_HOWTO, revision 1.1.1.1
1.1 misho 1: Creating an object
2: ------------------
3:
4: Object can be created in the following ways:
5:
6: 1. As a result of a function call. E.g.:
7:
8: $foo = create_new_foo("parameter");
9: $foo->run();
10:
11: The function should create a new zval, create new object and get the
12: handle for it, set handle and handler table as needed. Note that the
13: handle is the only ID of the object, so it should be enough to
14: identify it.
15:
16: 2. Overriding create_object handler for class. E.g.:
17:
18: $foo = new Java("some.Class.here", "parameter");
19: $foo->run();
20:
21: The create_object handler function should create a new zval, create
22: new object and get the handle for it, set handle and handler table as
23: needed, and also provide constructor method that would handle
24: constructor call. The get_constructor handler table entry should be
25: used for that. Do not rely class entry's constructor, unless you refer
26: to it from get_constructor handler.
27:
28: Object maintenance
29: ------------------
30:
31: The handlers add_ref and del_ref are called when a new zval referring
32: to the object is created. This does not create a new object - both
33: zvals still refer to the same object.
34:
35: clone_obj handler should create a new object, identical to an old one,
36: but being a separate entity.
37:
38: delete_obj should destroy an object, all references to it become
39: invalid.
40:
41: Object access - read
42: --------------------
43:
44: read_property is used to read object's property. This value is not
45: meant to be changed. The handler returns zval * with the value.
46:
47: Object access - write
48: ---------------------
49:
50: write_property is used to directly write object's property by
51: name. This handler is used to assign property variables or to change them
52: in operations like += or ++ (unless get_property_zval_ptr is also set).
53:
54: get_property_zval_ptr is used to obtain pointer to modifiable zval for
55: operations like += or ++. This should be used only if your object model
56: stores properties as real zval's that can be modified from outside.
57: Otherwise this handler should be NULL and the engine will use
58: read_property and write_property instead.
59:
60: get_property_ptr is used to obtain zval ** for future writing to
61: it. If your object properties are stored as zval*, return real place
62: where the property is stored. If the aren't, the best way is to create
63: proxy object and handle it via get and set methods (see below).
64: This method is meant to be used for send-by-reference and assign-by-reference
65: use of object properties. If you don;t want to implement property
66: referencing for your objects, you can set this handler to NULL.
67:
68: get and set handlers are used when engine needs to access the object
69: as a value. E.g., in the following situation:
70:
71: $foo =& $obj->bar;
72: $foo = 1;
73:
74: if $foo is an object (e.g., proxy object from get_property_ptr) it
75: would be accessed using write handler.
76:
77: Object access - method call
78: ---------------------------
79:
80: get_method handler is used to find method description by name. It
81: should set right type, function name and parameter mask for the
82: method. If the type is ZEND_OVERLOADED_FUNCTION, the method would be
83: called via call_method handler, otherwise it would be called with
84: standard Zend means.
85:
86: get_constructor performs the same function as get_method, but for the
87: object constructor.
88:
89: call_method handler is used to perform method call. Parameters are
90: passed like to any other Zend internal function.
91:
92: Object - comparison
93: -------------------
94:
95: Objects can be compared via compare_objects handler. This is used with
96: == operation, === compares objects by handles, i.e., return true if
97: and only if it's really the same object. Note that objects from
98: different object types (i.e., having different handlers) can not be
99: compared.
100:
101: Objects - reflection
102: --------------------
103:
104: get_class_name is used to retrieve class name of the object.
105: get_class_entry returns class entry (zend_class_entry) for the object,
106: in case there exists PHP class for it.
107: No other reflection functions are currently implemented.
108:
109: Objects - data structures and handlers
110: ---------------------------------------
111:
112: The object is represented by the following structure:
113:
114: struct _zend_object_value {
115: zend_object_handle handle;
116: zend_object_handlers *handlers;
117: };
118:
119: handle is an ID of the object among the objects of the same type (not
120: class!). The type of the object and how it behaves is determined by
121: the handler table.
122:
123: typedef struct _zend_object_handlers {
124: zend_object_add_ref_t add_ref;
125: zend_object_del_ref_t del_ref;
126: zend_object_delete_obj_t delete_obj;
127: zend_object_clone_obj_t clone_obj;
128: zend_object_read_property_t read_property;
129: zend_object_write_property_t write_property;
130: zend_object_get_property_ptr_t get_property_ptr;
131: zend_object_get_property_zval_ptr_t get_property_zval_ptr;
132: zend_object_get_t get;
133: zend_object_set_t set;
134: zend_object_has_property_t has_property;
135: zend_object_unset_property_t unset_property;
136: zend_object_get_properties_t get_properties;
137: zend_object_get_method_t get_method;
138: zend_object_call_method_t call_method;
139: zend_object_get_constructor_t get_constructor;
140: zend_object_get_class_entry_t get_class_entry;
141: zend_object_get_class_name_t get_class_name;
142: zend_object_compare_t compare_objects;
143: } zend_object_handlers;
144:
145: See zend_object_handlers.h for prototypes. All objects are passed as zval's.
146:
147: Handlers explained:
148:
149: add_ref - called when a copy of the object handle is created.
150:
151: del_ref - called when a copy of the object handle is destroyed.
152:
153: delete_obj - called when an object needs to be destroyed.
154:
155: clone_obj - called when a new object identical to an old one should be
156: created (unlike Zend Engine 1, this never happens unless explicitly
157: asked for).
158:
159: read_property - returns zval *, containing the value of the
160: property. Is used when value of the property should be retrieved for
161: reading.
162:
163: write_property - assigns value to certain property of the object.
164:
165: get_property_zval_ptr - retrieves zval** for being directly modified by
166: the engine. If your properties are not zval's, don't define it.
167:
168: get_property_ptr - retrieves zval** for the property of the value, to
169: be used for read and write. If object properties are not zval's
170: natively, this method should create and return proxy object for use
171: with get and set methods.
172:
173: get - retrieves zval* for object contents. To be used mainly with
174: proxy objects from get_property_ptr, but also may be used for
175: convert_to_* functions.
176:
177: set - sets value for object contents. To be used mainly with
178: proxy objects from get_property_ptr.
179:
180: has_property - checks if the object has certain property set.
181:
182: unset_property - removes value for the property of the object
183:
184: get_method - retrieves description of the method
185:
186: call_method - calls the method (parameters should be put on stack like
187: for any other PHP internal function).
188:
189: get_constructor - get description for the object constructor method
190:
191: get_class_entry - should return the class entry for the object
192:
193: get_class_name - get the name of the class the object belongs to
194:
195: compare_objects - compares if two objects are equal
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