[Translation][php extension development and embedded] Chapter 11 -php5 objects
黄舟
Release： 2023-03-05 16:26:01
Original
1478 people have browsed it
php5 objects
##It’s a bit confusing to compare php5 objects with their predecessors, php4 objects. Fair enough, but the API functions used by php5 objects are still built according to the API of php4. If you have read Chapter 10 "php4 Objects", you will be somewhat familiar with the content of this chapter. Before starting this chapter, you can like Chapter 10 Same as the beginning, rename the extension to sample3 and clean up the redundant code, leaving only the skeleton code of the extension.
Evolutionary History
There are two key components in php5 object variables. The first is a numerical identifier, which is very similar to the numerical resource ID introduced in Chapter 9 "Resource Data Type", and plays a role used in The role of the key to find the object instance in the corresponding table. The elements in this instance table contain references to zend_class_entry and the internal attribute table.
The second element is the object variable A handle table that allows you to customize how the Zend Engine handles instances. You will see this handle table later in this chapter.
zend_class_entry
A class entry is an internal representation of a class you define in user space. As you saw in the previous chapter, this structure is initialized by calling INIT_CLASS_ENTRY() with the class name and its function table. Next Use zend_register_internal_class() to register in the MINIT phase.
If you have read the previous chapter, You might be thinking "Looks pretty much the same so far?", and so far, you'd be right. Now let's start defining some object methods. You'll start to see some very definite and welcome differences.
The PHP_METHOD() macro was introduced in Zend Engine 2. It is an encapsulation of the PHP_FUNCTION() macro. It combines the class name and method name without manually defining the method like in php4. By using this macro, the namespace resolution specification of your code in the extension is consistent with that of other maintainers' code.
Definition
Define the implementation of a method, just like other functions, except that it is connected to the function table of the class. In addition to the PHP_METHOD() macro used for implementation, there are some new Macros can be used in the definition of function lists.
PHP_ME(classname, methodname, arg_info, flags)
Compared with the PHP_FE() macro introduced in Chapter 5 "Your First Extension", PHP_ME() adds a classname parameter and a flags parameter at the end (used to provide public, protected , private, static and other access controls, as well as abstract and other options). For example, to define the helloWorld method, you can define it as follows:
is very similar to the PHP_FALIAS() macro. This macro allows you to give the method described by the alias parameter (in the same class ) implementation provides a new name specified by name. For example, to copy your helloWorld method, you can define it as follows
.This is the same as the visibility of the php4 method
##ZEND_ACC_PROTECTED
Can only be called in a class or its subclass
ZEND_ACC_PRIVATE
can only be called in a class
For example, since the Sample3_SecondClass::helloWorld() method you defined earlier does not require an object instance, you can change its definition from simple Change ZEND_ACC_PUBLIC to ZEND_ACC_PUBLIC | ZEND_ACC_STATIC, so that the engine will not provide (instance) after knowing it.
Magic method
In addition to the magic methods of ZE1, ZE2 has added many new magic methods, as shown in the following table (or can be found at http://www.php.cn/)
Method
Usage
__construct(...)
Optional automatically called object constructor(The method previously defined is the same as the class name).If__construct() and classname()Both implementations exist,In the instantiation During the process, , will give priority to calling __construct()
# #__destruct()
When the instance leaves the scope,or requests the entire termination , will cause the __destruct() method of the instance to be implicitly called to handle some cleanup work, For example, closing a file or network handle.
__clone()
##By default,All instances are true pass-by-reference.In php5, If you want to truly copy an object instance, you must useclonekeyword.When the clone keyword is called on an object instance,
The __clone() method will be executed implicitly,It allows the object to copy some required internal resource data.
##__toString()
When using text to represent an object
,For example, when using the echo or print statement directly on the object,
The __toString() method will be automatically called by the engine.If the class implements this magic method,should return A string containing a description of the object's current state .
__get($var)
If the script requests an invisible attribute of an object(does not exist or is invisible due to access control )hour,
__get()The magic method will be called,The only parameter is the requested attribute name.implementation You can use its own internal logic to determine the most reasonable return value to return .
__set($var , $value)
is very similar to __get(),
__set()Provides the opposite ability,It is used to handle the logic when assigning invisible properties to objects. Implementations of __set() may choose to implicitly create these variables in standard attribute tables,set values using other storage mechanisms, Or throw an error directly and discard the value.
##__call($fname, $args)
When calling undefined methods of an object, you can achieve beautiful results by using the
__call() magic method Processing.This method accepts two parameters:The name of the called method,Array containing the numeric indices of all arguments passed when calling .
__isset($varname )
php5.1.0After, the call of isset($obj->prop) is not only a check# Is there prop in ##$obj? , will also call __isset()method,Dynamic evaluation try to use dynamic Whether the __get() and __set() methods can successfully read and write properties
__unset($varname)
## Similar to
__isset(), php 5.1 .0
Introduces a simple OOP interface for the unset() function ,It can be used for object properties,Although this property may not exist in the object's standard property table,But it might make sense for the dynamic property space of __get() and __set(),Therefore, __unset() is introduced to solve this problem. ##
get_property_ptr_ptr() is a variant of read_property(), which allows the calling scope to directly replace the current zval * with a new one. The default behavior is to return the standard property table The pointer address of the attribute in . If it does not exist, and there is no __get()/__set() magic method, the pointer is implicitly created and returned. If the __get() or __set() method exists, it will cause this handle to fail , causing the engine to instead rely on separate read_property and write_property calls.
##zval *read_dimension(zval *obj, zval *idx, int type TSRMLS_DC)
read_dimension () and write_dimension() are similar to the corresponding read_property() and write_property(); but they are triggered when the object is accessed as an array using the $obj['idx'] method. If the object's class does not implement the ArrayAccess interface, the default The behavior is to trigger an error; otherwise it calls the magic methods offsetget($idx) or offsetset($idx, $value).
##zval *get( zval *obj TSRMLS_DC)
void set(zval *obj, zval *value TSRMLS_DC)
When setting or retrieving the value of an object, the get() or set() method will be called on the object. The object itself is passed as the first parameter. For set, the new value is passed as the second parameter. ; Actually, these methods are used in arithmetic operations. There is no default handler for these operations.
##int has_property(zval *obj, zval *prop, int chk_type TSRMLS_DC)
#This handler is called when isset() is called on an object property. By default the standard processor will check the prop specified Attribute name. If this attribute is not found in PHP 5.1.0 and the __isset() method is defined, this method will be called. If the value of the chk_type parameter is 2, then only the attribute needs to exist. If the value of chk_type is 0, then Must exist and must not be a value of IS_NULL. If the chk_type value is 1, the attribute must exist and must be a value other than FALSE. Note: In PHP 5.0.x,
The meaning of chk_type is consistent with the chk_type of has_dimension.
##int has_dimension(zval *obj, zval *idx, int chk_type TSRMLS_DC)
When calling isset() when treating an object as an array (such as isset($obj['idx'])), this processor is used. The default standard processor will check whether the object is implemented If the ArrayAccess interface is implemented, the offsetexists($idx) method is called. If not found (referring to calling offsetexists()), it is the same as if the offsetexists() method is not implemented, and 0 is returned. Otherwise, if chk_type is 0, return directly true(1). A chk_type of 1 indicates that it must call the offsetget($idx) method of the object and test the return value,
Check whether the value is FALSE before returning TRUE(1).
These two methods when trying to unload object attributes ( or when applying unset() to an object in an array). The unset_property() handler either removes the property from the standard property table (if it exists), or attempts to call the implemented __unset($prop) method (php 5.1. 0), unset_dimension() calls the offsetunset($idx) method when the class implements ArrayAccess.
##HashTable *get_properties(zval *obj TSRMLS_DC)
This processor is actually called when the internal function uses the Z_OBJPROP() macro to read properties from the standard property table. The default processing of PHP objects The processor unpacks and returns Z_OBJ_P(object)->properties, which is the real standard property table.
##union _zend_function *get_method(zval **obj_ptr char *method_name, int methodname_len TSRMLS_DC)
This handler is called when parsing an object method in the class's function_table. If the method does not exist in the main function_table, the default handler returns a pointer to the object. _call($name, $args) method wrapped zend_function * pointer.
Function defined as ZEND_OVERLOADED_FUNCTION type will be executed as call_method processor. By default, this processor is undefined.
union _zend_function *get_constructor(zval *obj TSRMLS_DC)
Similar to the get_method() processor, this processor returns a corresponding object method Reference. The constructor in the zend_class_entry of the class is stored in a special way, which makes it special. Overriding of this method is very rare.
Similar to get_constructor(), this processor is rarely overridden. Its purpose is to map an object instance Return to its original class definition.
##int get_class_name(zval *object, char **name zend_uint *len, int parent TSRMLS_DC)
get_class_entry() is one step of get_class_name(). After getting the zend_object of the object, it will use the object’s class name or its parent class name (this depends on the value of the parameter parent ) returns a copy. The returned copy of the class name must use non-persistent storage (emalloc()).
int compare_objects(zval *obj1, zval * obj2 TSRMLS_DC)
When comparison operators (for example: ==, !=, <=, <, >, >=) are used in When there are two objects, calling compare_objects() on the operands (the two objects participating in the comparison) is the first part of this work. Its return value is usually 1, 0, -1, which represents greater than, equal to, and less than respectively. By default, objects are compared based on their standard property tables, using the same comparison rules as the array comparison rules learned in Chapter 8, "Working with Arrays and HashTables".
int cast_object(zval *src, zval *dst, int type, int should_free TSRMLS_DC)
When trying to cast the object to other data type, this processor will be triggered. If should_free is set to a non-zero value, zval_dtor() will be called on dst, first releasing the internal resources. In short, the processor should try to represent the object in src as dst to Out of the type of zval *. This handler is undefined by default, but when it is present, it should return SUCCESS or FAILURE.
int count_elements (zval *obj, long *count TSRMLS_DC)
Objects that implement array access should define this processor, which will set the current number of elements to count and returns SUCCESS. If the current instance does not implement array access, it should return FAILURE to cause the engine to go back and check the standard attribute table.
Translation Note: The above handle table and The php-5.4.9 used by the translator is no longer completely consistent. When studying this part, readers can refer to the standard processor handle table at the bottom in Zend/zend_object_handlers.c.
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
