php对象的实现

1.对象的数据结构很是简单

typedef struct _zend_object     zend_object;

struct _zend_object {
    zend_refcounted_h gc; //引用计数
    uint32_t          handle;
    zend_class_entry *ce; //所属类
    const zend_object_handlers *handlers; //对象操做处理函数
    HashTable        *properties;
    zval              properties_table[1]; //普通属性值数组
};

          handle: 一次request期间对象的编号，每一个对象都有一个惟一的编号，与建立前后顺序有关，主要在垃圾回收时用

         ce: 所属类的zend_class_entry

         handlers: 这个保存的对象相关操做的一些函数指针，好比成员属性的读写、成员方法的获取、对象的销毁/克隆等等，这些操做接口都有默认的函数

struct _zend_object_handlers {
    int                                     offset;
    zend_object_free_obj_t                  free_obj; //释放对象
    zend_object_dtor_obj_t                  dtor_obj; //销毁对象
    zend_object_clone_obj_t                 clone_obj;//复制对象
    
    zend_object_read_property_t             read_property; //读取成员属性
    zend_object_write_property_t            write_property;//修改为员属性
    ...
}

//默认值处理handler
ZEND_API zend_object_handlers std_object_handlers = {
    0,
    zend_object_std_dtor,                   /* free_obj */
    zend_objects_destroy_object,            /* dtor_obj */
    zend_objects_clone_obj,                 /* clone_obj */
    zend_std_read_property,                 /* read_property */
    zend_std_write_property,                /* write_property */
    zend_std_read_dimension,                /* read_dimension */
    zend_std_write_dimension,               /* write_dimension */
    zend_std_get_property_ptr_ptr,          /* get_property_ptr_ptr */
    NULL,                                   /* get */
    NULL,                                   /* set */
    zend_std_has_property,                  /* has_property */
    zend_std_unset_property,                /* unset_property */
    zend_std_has_dimension,                 /* has_dimension */
    zend_std_unset_dimension,               /* unset_dimension */
    zend_std_get_properties,                /* get_properties */
    zend_std_get_method,                    /* get_method */
    NULL,                                   /* call_method */
    zend_std_get_constructor,               /* get_constructor */
    zend_std_object_get_class_name,         /* get_class_name */
    zend_std_compare_objects,               /* compare_objects */
    zend_std_cast_object_tostring,          /* cast_object */
    NULL,                                   /* count_elements */
    zend_std_get_debug_info,                /* get_debug_info */
    zend_std_get_closure,                   /* get_closure */
    zend_std_get_gc,                        /* get_gc */
    NULL,                                   /* do_operation */
    NULL,                                   /* compare */
}

 

 

            properties: 普通成员属性哈希表，对象建立之初这个值为NULL

            properties_table: 成员属性数组，它是一个数组，zend_object是个变长结构体，分配时会根据非静态属性的数量肯定其大小

            普通成员属性的查找比较容易理解，首先是从zend_class的属性信息哈希表中找到zend_property_info，并判断其可见性(public、private、protected)，若是能够访问则直接根据属性的offset在zend_object.properties_table数组中取到属性值