## 示例
### 用PHP实现
```php
<?php
const TEMP_CONVERTER_TO_CELSIUS = 1;
const TEMP_CONVERTER_TO_FAHREINHEIT = 2;
//华氏转摄氏
function fahrenheit_to_celsius($fahrenheit){
return 5/9 * ($fahrenheit - 32);
}
//摄氏转华氏
function celsius_to_fahrenheit($celsius){
return 9/5 * $celsius + 32;
}
//双向转换
function temperature_converter($temp, $type = TEMP_CONVERTER_TO_CELSIUS){
switch ($type) {
case TEMP_CONVERTER_TO_CELSIUS:
return sprintf("华氏 %.2f 度, 摄氏 %.2f 度", $temp, fahrenheit_to_celsius($temp));
case TEMP_CONVERTER_TO_FAHREINHEIT:
return sprintf("摄氏 %.2f 度, 华氏 %.2f 度", $temp, celsius_to_fahrenheit($temp));
default:
trigger_error("转换模式参数错误, 可接受的转换模式值为 1 或 2", E_USER_WARNING);
break;
}
}
//华氏数组批量转摄氏
function multiple_fahrenheit_to_celsius(array $temperatures){
foreach ($temperatures as $temp) {
$return[] = fahreinheit_to_celsius($temp);
}
return $return;
}
```
### 用扩展实现
1. 生成骨架.
`./ext_skel --extname=pib --proto=./pib_proto --no-help`
pib_proto:
```
double fahrenheit_to_celsius (double f)
double celsius_to_fahrenheit (double c)
string temperature_converter (double t, long mode)
array multiple_fahrenheit_to_celsius(array temperatures)
```
2. 编写代码 : 代码在./code/1-5-2/pib
3. 编译测试
**编译：**
```shell
cd ext/pib
../../../php-7-1-8-install/bin/phpize
./configure --with-php-config=../../../php-7-1-8-install/bin/php-config
make
```
**运行时配置**
**扩展测试**
```php
<?php
echo celsius_to_fahrenheit(35);
echo fahrenheit_to_celsius(95);
echo temperature_converter(95,1);
print_r(multiple_fahrenheit_to_celsius(array(94,69,120)));
//查看扩展的反射信息,等于命令行中执行 php -dextension=pib.so --re pib
//如果不声明参数的话，反射获取不到参数信息
//print_r(ReflectionExtension::export('pib'));
```
### 扩展中的常量
```c
/* 常量的数据结构 */
typedef struct _zend_constant {
zval value;
zend_string *name;
int flags;
int module_number;
} zend_constant;
/* 注册常量的宏: */
/* 注册NULL常量 */
#define REGISTER_NULL_CONSTANT(name, flags) \
zend_register_null_constant((name), sizeof(name)-1, (flags), module_number)
/* 注册bool常量 */
#define REGISTER_BOOL_CONSTANT(name, bval, flags) \
zend_register_bool_constant((name), sizeof(name)-1, (bval), (flags), module_number)
/* 注册整形常量 */
#define REGISTER_LONG_CONSTANT(name, lval, flags) \
zend_register_long_constant((name), sizeof(name)-1, (lval), (flags), module_number)
/* 注册浮点型常量 */
#define REGISTER_DOUBLE_CONSTANT(name, dval, flags) \
zend_register_double_constant((name), sizeof(name)-1, (dval), (flags), module_number)
/* 注册字符串常量，str类型为char* */
#define REGISTER_STRING_CONSTANT(name, str, flags) \
zend_register_string_constant((name), sizeof(name)-1, (str), (flags), module_number)
/* 注册字符串常量，截取指定长度，str类型为char* */
#define REGISTER_STRINGL_CONSTANT(name, str, len, flags) \
zend_register_stringl_constant((name), sizeof(name)-1, (str), (len), (flags), module_number)
```
#### TODO::扩展测试脚本的编写
http://qa.php.net/write-test.php
### 练习
https://github.com/ThomasWeinert/php-extension-sample
https://github.com/Leon2012/php-ext
https://github.com/wzx19840423/php-extension/tree/master/src
### 跟踪调试扩展
## 参考资料:
http://www.phpinternalsbook.com/index.html
https://github.com/pangudashu/php7-internal/
https://github.com/tvlooy/php-ext-dev-book
