Original: PHP kernel research and other implementations

I’ve been quite busy these days. I don’t have time to write. I’ll write a few more articles during the weekend.
Most languages ​​currently support classes.
What are classes? Classes are object-oriented, or OOP for short. The English name is Object Oriented Programming.
What is object-oriented? It is a programming architecture.
A basic principle of OOP is that a computer program is composed of a single unit or object that can function as a subroutine. OOP achieves three goals of software engineering: Reusability , flexibility and scalability.
Because what we are talking about is not just a simple description here. If you don’t know what a class is and what is object-oriented... then this article is not suitable for you at the moment.

classPerson{

};

​

The above is to create a PHP class. class is the keyword of PHP. Through it we can find out how Zend creates the class. class_entry_type T_STRING extends_from

                                                                                                            ​                                                                                                                                              LS_CC); }

    | interface_entry T_STRING​​​                                                                                                                                TSRMLS_CC); }

;

class_entry_type :

                                                                                                             CG(zend_lineno); $$. u.EA.type = ZEND_ACC_EXPLICIT_ABSTRACT_CLASS; }

|

T_CLASS, T_ABSTRACT T_CLASS and T_FINAL are the three modes of PHP

T_CLASS: It is a standard class.

T_ABSTRACT: It declares an abstract class

T_FINAL: It declares a class that does not allow inheritance and extension.

Of course there is also interface

They are defined in Zend In the file /zend_complie.h

#define ZEND_ACC_IMPLICIT_ABSTRACT_CLASS 0x10 //Not declared as abstract, but there are abstract methods inside

#define ZEND_ACC_EXPLICIT_ABSTRACT_CLASS 0x20 //Abstract

#define ZEND _ACC_FINAL_CLASS 0x40 //Final

#define ZEND_ACC_INTERFACE 0x80 //Interface

These three rules record the current line and set the type of the class.
When defining the class, the two methods zend_do_begin_class_declaration and zend_do_end_class_declaration are called.
The keyword of the class, the name of the class and the inherited parent class are passed as parameters to this Two functions.
zend_do_begin_class_declaration is used to declare a class, set the type, and create a
zend_do_end_class_declaration to process the attributes and methods in the class.
Before talking about the two functions, we must first talk about the structure of the saved class zend_class_entry
It defines In Zend/zend.h

struct_zend_class_entry {

                                                                    struct_zend_class_entry *parent;//Inherited parent class

intrefcount; //Number of references

              zend_bool constants_updated                                    HashTable default_properties;//Properties

B Hashtable Properties_info; // The access level of the function

hashtable default_Static_members; // Static members

havetable *static_members; _Static_members, the built -in class is null

hashtable constants_table;

C Construct_zend_function_ENTRY *Builtin_functions;

// Is it familiar ??? The magic function is here ...

union_function *constructor; UCTOR; n Union_zend_function *Clone;

Union_zend_function *__ GET;

union_zend_function *__set;

          union_zend_function *__unset; 

         union_zend_function *__isset; 

            union_zend_function *__call;

          union_zend_function *__tostring;

                                                                           with with with with with with with, with zend_class_iterator_funcs iterator_funcs;

                                                                                        ’ (*get_iterator)(zend_class_entry *ce, zval *object,intby_ref TSRMLS_DC);

   int (*interface_gets_implemented)(zend_class_entry *iface, zend_class_entry *class_type TSRMLS_DC);/* a class implements this interface */

      union_zend_function *(*get_static_method)(zend_class_entry *ce,char* method,intmethod_len TSRMLS_DC);

/ * serializer callbacks */

int(*serialize)(zval *object, unsignedchar**buffer, zend_uint *buf_len, zend_serialize_data *data TSRMLS_DC);

int(*unserialize)(zval **object, zend_class_entry *ce,constunsignedchar *buf, zend_uint buf_len, zend_unserialize_data *data TSRMLS_DC); char*filename; //Declare the file address of the class

        zend_uint line_start; // Class start Line

            zend_uint line_end; // Class end line

        char*doc_comment;

                                                    ‐                         

  

        struct_zend_module_entry *module;

};

   

清楚了这个结构之后 下面来看看zend_do_begin_class_declaration函数

   

voidzend_do_begin_class_declaration(constznode *class_token, znode *class_name,constznode *parent_class_name TSRMLS_DC)/* {{{ */

{

        zend_op *opline;

        intdoing_inheritance = 0;

        zend_class_entry *new_class_entry;

        char*lcname;

        interror = 0;

        zval **ns_name;

  

        if(CG(active_class_entry)) {

                zend_error(E_COMPILE_ERROR,"Class declarations may not be nested");

                return;

        }

  

        lcname = zend_str_tolower_dup(class_name->u.constant.value.str.val, class_name->u.constant.value.str.len);

  

        if(!(strcmp(lcname,"self") &&strcmp(lcname,"parent"))) {

                efree(lcname);

                zend_error(E_COMPILE_ERROR,"Cannot use '%s' as class name as it is reserved", class_name->u.constant.value.str.val);

        }

  

        /* Class name must not conflict with import names */

        if(CG(current_import) &&

                        zend_hash_find(CG(current_import), lcname, Z_STRLEN(class_name->u.constant)+1, (void**)&ns_name) == SUCCESS) {

                error = 1;

        }

       if(CG(current_namespace)) {

                /* Prefix class name with name of current namespace */

                znode tmp;

  

                tmp.u.constant = *CG(current_namespace);

                zval_copy_ctor(&tmp.u.constant);

                zend_do_build_namespace_name(&tmp, &tmp, class_name TSRMLS_CC);

                class_name = &tmp;

                efree(lcname);

                lcname = zend_str_tolower_dup(Z_STRVAL(class_name->u.constant), Z_STRLEN(class_name->u.constant));

        }

  

        if(error) {

                char*tmp = zend_str_tolower_dup(Z_STRVAL_PP(ns_name), Z_STRLEN_PP(ns_name));

  

                if(Z_STRLEN_PP(ns_name) != Z_STRLEN(class_name->u.constant) ||

                        memcmp(tmp, lcname, Z_STRLEN(class_name->u.constant))) {

                        zend_error(E_COMPILE_ERROR,"Cannot declare class %s because the name is already in use", Z_STRVAL(class_name->u.constant));

                }

                efree(tmp);

        }

  

        new_class_entry = emalloc(sizeof(zend_class_entry));

        new_class_entry->type = ZEND_USER_CLASS;

        new_class_entry->name = class_name->u.constant.value.str.val;

        new_class_entry->name_length = class_name->u.constant.value.str.len;

  

        zend_initialize_class_data(new_class_entry, 1 TSRMLS_CC);

        new_class_entry->filename = zend_get_compiled_filename(TSRMLS_C);

        new_class_entry->line_start = class_token->u.opline_num;

        new_class_entry->ce_flags |= class_token->u.EA.type;

if(parent_class_name && parent_class_name->op_type != IS_UNUSED) {

                switch(parent_class_name->u.EA.type) {

                        caseZEND_FETCH_CLASS_SELF:

                                zend_error(E_COMPILE_ERROR,"Cannot use 'self' as class name as it is reserved");

                                break;

                        caseZEND_FETCH_CLASS_PARENT:

                                zend_error(E_COMPILE_ERROR,"Cannot use 'parent' as class name as it is reserved");

                                break;

                        caseZEND_FETCH_CLASS_STATIC:

                                zend_error(E_COMPILE_ERROR,"Cannot use 'static' as class name as it is reserved");

                                break;

                        default:

                                break;

                }

                doing_inheritance = 1;

        }

  

        opline = get_next_op(CG(active_op_array) TSRMLS_CC);

        opline->op1.op_type = IS_CONST;

        build_runtime_defined_function_key(&opline->op1.u.constant, lcname, new_class_entry->name_length TSRMLS_CC);

  

        opline->op2.op_type = IS_CONST;

        opline->op2.u.constant.type = IS_STRING;

        Z_SET_REFCOUNT(opline->op2.u.constant, 1);

  

        if(doing_inheritance) {

                opline->extended_value = parent_class_name->u.var;

                opline->opcode = ZEND_DECLARE_INHERITED_CLASS;

        }else{

                opline->opcode = ZEND_DECLARE_CLASS;

        }

opline->op2.u.constant.value.str.val = lcname;

        opline->op2.u.constant.value.str.len = new_class_entry->name_length;

  

        zend_hash_update(CG(class_table), opline->op1.u.constant.value.str.val, opline->op1.u.constant.value.str.len, &new_class_entry,sizeof(zend_class_entry *), NULL);

        CG(active_class_entry) = new_class_entry;

  

        opline->result.u.var = get_temporary_variable(CG(active_op_array));

        opline->result.op_type = IS_VAR;

        CG(implementing_class) = opline->result;

  

        if(CG(doc_comment)) {

                CG(active_class_entry)->doc_comment = CG(doc_comment);

                CG(active_class_entry)->doc_comment_len = CG(doc_comment_len);

                CG(doc_comment) = NULL;

                CG(doc_comment_len) = 0;

        }

}

   

lcname = zend_str_tolower_dup(class_name->u.constant.value.str.val, class_name->u.constant.value.str.len);
把所有类全部转换为小写处理.这就是为什么PHP大小写不敏感的原因.
if (!(strcmp(lcname, “self”) && strcmp(lcname, “parent”))) {
efree(lcname);
zend_error(E_COMPILE_ERROR, “Cannot use ‘%s’ as class name as it is reserved”, class_name->u.constant.value.str.val);
}
类的名字不能是self和parent.
第23-26行 用来检测类名是否重复定义.
第27-37行 用来设置命名空间,这是PHP5.3的新特性
第39-47行 用来抛出重复定义的错误
第49-57行 初始化保存类的结构
zend_initialize_class_data(new_class_entry, 1 TSRMLS_CC);函数是用来初始化结构里面的HashTable,魔术方法.
这个函数里面也有上面提到( HashTable *static_members; //静态成员,当是用户声明的类等于default_static_members,内置的类为NULL)的原因
第58-73行 同样用来检测父类的类名是否包含 保留关键字 self,parent,static
剩下的就是用来生成一个OP,
是内部类:那么生成的OP中间代码就是 ZEND_DECLARE_INHERITED_CLASS
是用户类:OP中间代码就是ZEND_DECLARE_CLASS
在这之后..Zend引擎会调用zend_execute函数执行OP的中间代码ZEND_DECLARE_CLASS_SPEC_HANDLER
它定义在Zend/zend_vm_execute.h中.
这个函数将执行关键代码
EX_T(opline->result.u.var).class_entry = do_bind_class(opline, EG(class_table), 0 TSRMLS_CC) ;
do_bind_class会将此类放到class_table中.当然 ,在这个函数里还会判断该类是否存在.不存在会抛出错误
Internal Zend error – Missing class information for %s
如果存在 则会添加成功
那么到这里类就创建成功了.
下一张节就要深入到 类内部了哦…

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