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Update 6.2.md #158

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17 changes: 15 additions & 2 deletions 6.2.md
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,7 @@ byref_compiletime_arginfo是一个arginfo结构体，我们在前面的章节中

<div class="tip-common">原书中此处有arginfo在PHP4里的实现，被我略去了。</div>
在Zend Engine 2 (PHP5+)中，arginfo的数据是由多个zend_arg_info结构体构成的数组，数组的每一个成员即每一个zend_arg_info结构体处理函数的一个参数。zend_arg_info结构体的定义如下：

````c
typedef struct _zend_arg_info {
const char *name; /* 参数的名称*/
Expand All @@ -84,6 +85,7 @@ typedef struct _zend_arg_info {

````
生成zend_arg_info结构的数组比较繁琐，为了方便PHP扩展开发者，内核已经准备好了相应的宏来专门处理此问题，首先先用一个宏函数来生成头部，然后用第二个宏生成具体的数据，最后用一个宏生成尾部代码。

````c
#define ZEND_BEGIN_ARG_INFO(name, pass_rest_by_reference) ZEND_BEGIN_ARG_INFO_EX(name, pass_rest_by_reference, ZEND_RETURN_VALUE, -1)
#define ZEND_BEGIN_ARG_INFO_EX(name, pass_rest_by_reference, return_reference, required_num_args) \
Expand All @@ -97,20 +99,27 @@ typedef struct _zend_arg_info {
#define ZEND_ARG_ARRAY_INFO(pass_by_ref, name, allow_null) { #name, sizeof(#name)-1, NULL, 0, 1, allow_null, pass_by_ref, 0, 0 },


#define ZEND_END_ARG_INFO() };
#define ZEND_END_ARG_INFO()

};

````

```
//这里我们先看
ZEND_BEGIN_ARG_INFO(name, pass_rest_by_reference)
ZEND_BEGIN_ARG_INFO_EX(name, pass_rest_by_reference, return_reference,required_num_args)
```

````
这两个宏函数的前两个参数的含义是一样的，name便是这个zend_arg_info数组变量的名字，这里我们定义它为：byref_compiletime_arginfo。pass_rest_by_reference如果被赋值为1，则代表着所有的参数默认都是需要以引用的方式传递的(在arginfo中单独声明的除外)。而对于ZEND_BEGIN_ARG_INFO_EX的后两个参数：
<ul>
<li>name和pass_rest_by_reference的含义同上。</li>
<li>return_reference：声明这个函数的返回值需要以引用的形式返回，这个参数已经在前面章节用过了。</li>
<li>required_num_args：函数被调用时，传递参数至少为前N个函数(也就是后面参数都有默认值)，当设置为-1时，必须传递所有参数</li>
</ul>

接下来让我们看生成具体数据的宏：

````c
ZEND_ARG_PASS_INFO(by_ref)
//强制所有参数使用引用的方式传递
Expand All @@ -130,7 +139,9 @@ ZEND_BEGIN_ARG_INFO(byref_compiletime_arginfo, 0)
ZEND_END_ARG_INFO()

````

为了使我们的扩展能够兼容PHP4，还需要使用#ifdef进行特殊处理。

````c
#ifdef ZEND_ENGINE_2
ZEND_BEGIN_ARG_INFO(byref_compiletime_arginfo, 0)
Expand All @@ -141,7 +152,9 @@ static unsigned char byref_compiletime_arginfo[] = { 1, BYREF_FORCE };
#endif

````

我们copy一份ZEND_FUNCTION(byref_calltime)的实现，并重名成ZEND_FUNCTION(byref_compiletime)就行了。或者直接弄个ZEND_FALIAS就行了：

````c
ZEND_FALIAS(byref_compiletime,byref_calltime,byref_compiletime_arginfo)

Expand Down