PHP源码分析-面向对象(一)
在PHP中，面向对象与Class是密切相关的，来看看在内核中如何实现Class的接口、继承、私有、受保护、公开等特性。一、创建类
zend_class_entry是内核中定义的一个结构体，是PHP中类与对象的基础结构类型。
如何在扩展中定义myclass类，并能够在PHP中能够实例化？
PHP中看起来像这样：
<?php
$obj = new myclass();
?>
内核中：zend_class_entry *myclass;//定义全局指针变量，指向myclass类。
static zend_function_entry myclass_method[] = {//myclass中的方法
{NULL, NULL, NULL}
}
PHP_MINIT_FUNCTION(extension_name){
zend_class_entry class;
INIT_CLASS_ENTRY(class, "myclass", myclass_method);
myclass = zend_register_internal_class(&class TSRMLS_CC);
return SUCCESS;
}
某个类的zend_class_entry会经常用到，所以我们一般会把它保存在一个全局变量里，供扩展中其它地方的程序使用.
对应上述myclass类的实现，在PHP中的代码：
<?php
class myclass{
}
?>
这个类没有任何属性和方法。
二、创建类的属性
在介绍类的属性之前，先了解类中的public、protected、private在内核中的表示。
#define ZEND_ACC_STATIC 0x01 /* Static */
#define ZEND_ACC_PUBLIC 0x100 /* Public */
#define ZEND_ACC_PROTECTED 0x200 /* Protected */
#define ZEND_ACC_PRIVATE 0x400 /* Private */
定义类的属性可以使用内核提供的zend_declare_property_*系列函数，同时需要三个信息：
属性名称、属性默认值、属性访问权限。
<?php
class myclass{
private my_var="this is property";
}
?>
内核中：zend_class_entry *myclass;
static zend_function_entry myclass_method[] = {
{NULL, NULL, NULL}
}
PHP_MINIT_FUNCTION(extension_name){
zend_class_entry class;
INIT_CLASS_ENTRY(class, "myclass", myclass_method);
myclass = zend_register_internal_class(&class TSRMLS_CC);
zend_declare_property_string(myclass, "my_var", strlen("my_var"), "this is property", ZEND_ACC_PRIVATE TSRMLS_CC);
}
//内核中提供了定义类属性的宏
ZEND_API int zend_declare_property(zend_class_entry *ce, char *name, int name_length, zval *property, int access_type TSRMLS_DC);
ZEND_API int zend_declare_property_ex(zend_class_entry *ce, const char *name, int name_length, zval *property, int access_type, char *doc_comment, int doc_comment_len TSRMLS_DC);
ZEND_API int zend_declare_property_null(zend_class_entry *ce, char *name, int name_length, int access_type TSRMLS_DC);
ZEND_API int zend_declare_property_bool(zend_class_entry *ce, char *name, int name_length, long value, int access_type TSRMLS_DC);
ZEND_API int zend_declare_property_long(zend_class_entry *ce, char *name, int name_length, long value, int access_type TSRMLS_DC);
ZEND_API int zend_declare_property_double(zend_class_entry *ce, char *name, int name_length, double value, int access_type TSRMLS_DC);
ZEND_API int zend_declare_property_string(zend_class_entry *ce, char *name, int name_length, char *value, int access_type TSRMLS_DC);
ZEND_API int zend_declare_property_stringl(zend_class_entry *ce, char *name, int name_length, char *value, int value_len, int access_type TSRMLS_DC);
三、创建类中的方法
#define ZEND_ACC_STATIC 0x01 /* 静态方法 */
#define ZEND_ACC_ABSTRACT 0x02 /* 抽象方法 */
#define ZEND_ACC_FINAL 0x04 /* 终态方法 */
#define ZEND_ACC_IMPLEMENTED_ABSTRACT 0x08 /* fn_flags */
#define ZEND_ACC_INTERACTIVE 0x10 /* fn_flags */
#define ZEND_ACC_PUBLIC 0x100 /* PUBLIC */
#define ZEND_ACC_PROTECTED 0x200 /* PROTECTED */
#define ZEND_ACC_PRIVATE 0x400 /* PRIVATE */
#define ZEND_ACC_CHANGED 0x800 /* fn_flags, zend_property_info.flags */
#define ZEND_ACC_CTOR 0x2000 /* __construct */
#define ZEND_ACC_DTOR 0x4000 /* __destruct */
#define ZEND_ACC_CLONE 0x8000 /* __clone */
#define ZEND_ACC_ALLOW_STATIC 0x10000/* fn_flags */
#define ZEND_ACC_SHADOW 0x20000/* fn_flags */
#define ZEND_ACC_DEPRECATED 0x40000/* fn_flags */
#define ZEND_ACC_CLOSURE 0x100000 /* fn_flags */
#define ZEND_ACC_CALL_VIA_HANDLER 0x200000 /* fn_flags */在实现类中方法前，先了解一下zend_function_entry。
在新建的扩展中，有一个zend_function_entry，内核通过它把PHP语言中的函数和C语言编写的函数连接，zend_function_entry相当于桥梁。
class中，同样用它来连接PHP中类的方法与C语言编写的方法。
<?php
class myclass{
public function __construct(){
echo "init myclass!";
}
public function hello(){
echo "hello";
}
}
?>
内核中：
zend_class_entry *myclass;
PHP_METHOD(myclass, __construct){
php_printf("init myclass!");
}
PHP_METHOD(myclass, hello){
php_printf("hello");
}
static zend_function_entry myclass_method[] = {
ZEND_ME(myclass, __construct, NULL, ZEND_ACC_PUBLIC|ZEND_ACC_CTOR);
ZEND_ME(myclass, hello, NULL, ZEND_ACC_PUBLIC);
{NULL, NULL, NULL}
}
PHP_MINIT_FUNCTION(extension_name){
zend_class_entry class;
INIT_CLASS_ENTRY(class, "myclass", myclass_method);
myclass = zend_register_internal_class(&class TSRMLS_CC);
return SUCCESS;
}
四、创建类中的常量
使用内核提供的API即可。
ZEND_API int zend_declare_class_constant(zend_class_entry *ce, const char *name, size_t name_length, zval *value TSRMLS_DC);
ZEND_API int zend_declare_class_constant_null(zend_class_entry *ce, const char *name, size_t name_length TSRMLS_DC);
ZEND_API int zend_declare_class_constant_long(zend_class_entry *ce, const char *name, size_t name_length, long value TSRMLS_DC);
ZEND_API int zend_declare_class_constant_bool(zend_class_entry *ce, const char *name, size_t name_length, zend_bool value TSRMLS_DC);
ZEND_API int zend_declare_class_constant_double(zend_class_entry *ce, const char *name, size_t name_length, double value TSRMLS_DC);
ZEND_API int zend_declare_class_constant_stringl(zend_class_entry *ce, const char *name, size_t name_length, const char *value, size_t value_length TSRMLS_DC);
ZEND_API int zend_declare_class_constant_string(zend_class_entry *ce, const char *name, size_t name_length, const char *value TSRMLS_DC);
<?php
class myclass{
const class_name = "myclass";
}
?>内核中：
zend_class_entry *myclass;
static zend_function_entry myclass_method[] = {
{NULL, NULL, NULL}
}
PHP_MINIT_FUNCTION(extension_name){
zend_class_entry class;
INIT_CLASS_ENTRY(class, "myclass", myclass_method);
myclass = zend_register_internal_class(&class TSRMLS_CC);
zend_declare_class_constant_stringl(myclass, "class_name", strlen("class_name"), "myclass", strlen("myclass") TSRMLS_CC);
}
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