PHP源碼分析-物件導向(一)

在PHP中，物件導向與Class是密切相關的，來看看在核心中如何?Class的介面、繼承、私人、受保護、公開等特性。

一、建立類
zend_class_entry是核心中定義的一個結構體，是PHP中類與對象的基礎結構類型。
如何在擴充中定義myclass類，並能夠在PHP中能夠執行個體化？

PHP中看起來像這樣：

<?php$obj = new myclass();?>

核心中：

zend_class_entry *myclass;//定義全域指標變數，指向myclass類。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;}

某個類的zend_class_entry會經常用到，所以我們一般會把它儲存在一個全域變數裡，供擴充中其它地方的程式使用.

對應上述myclass類的實現，在PHP中的代碼：

<?phpclass myclass{}?>

這個類沒有任何屬性和方法。

二、建立類的屬性

在介紹類的屬性之前，先瞭解類中的public、protected、private在核心中的表示。

#define ZEND_ACC_STATIC                     0x01     /* Static */#define ZEND_ACC_PUBLIC                     0x100    /* Public */#define ZEND_ACC_PROTECTED                  0x200    /* Protected */#define ZEND_ACC_PRIVATE                    0x400    /* Private */

定義類的屬性可以使用核心提供的zend_declare_property_*系列函數，同時需要三個資訊：
屬性名稱、屬性預設值、屬性存取權限。

<?phpclass myclass{private my_var="this is property";}?>

核心中：

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);}

//核心中提供了定義類屬性的宏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、建立類中的方法

#define ZEND_ACC_STATIC                     0x01     /* 靜態方法 */#define ZEND_ACC_ABSTRACT                   0x02     /* 抽象方法 */#define ZEND_ACC_FINAL                      0x04     /* 終態方法 */#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 */

在實作類別中方法前，先瞭解一下zend_function_entry。
在建立的擴充中，有一個zend_function_entry，核心通過它把PHP語言中的函數和C語言編寫的函數串連，zend_function_entry相當於橋樑。
class中，同樣用它來串連PHP中類的方法與C語言編寫的方法。

<?phpclass myclass{public function __construct(){echo "init myclass!";}public function hello(){echo "hello";}}?>

核心中：

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、建立類中的常量

使用核心提供的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);

<?phpclass myclass{const class_name = "myclass";}?>

核心中：

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);}