这篇文章，我们实现一个判断某个协程是否存在的接口：
Study\Coroutine::isExist(long $cid): bool我们先定义方法参数，在study_coroutine_util.cc文件中进行定义：
ZEND_BEGIN_ARG_INFO_EX(arginfo_study_coroutine_isExist, 0, 0, 1)
ZEND_ARG_INFO(0, cid)
ZEND_END_ARG_INFO()方法接收一个协程id。
然后实现这个接口：
PHP_METHOD(study_coroutine_util, isExist)
{
zend_long cid = 0;
bool is_exist;
ZEND_PARSE_PARAMETERS_START(1, 1)
Z_PARAM_LONG(cid)
ZEND_PARSE_PARAMETERS_END_EX(RETURN_FALSE);
auto coroutine_iterator = Coroutine::coroutines.find(cid);
is_exist = (coroutine_iterator != Coroutine::coroutines.end());
RETURN_BOOL(is_exist);
}我们直接在Coroutine::coroutines中查找这个协程是否存在，如果找到，则返回true；否则返回false。
因为上一章我们修复了一个协程死亡后，没有从Coroutine::coroutines中删除的bug，所以，我们的Study\Coroutine::isExist可以正常使用了。
我们编写测试脚本：
<?php
function task($arg)
{
$cid = Study\Coroutine::getCid();
echo "coroutine [{$cid}] create" . PHP_EOL;
Study\Coroutine::yield();
echo "coroutine [{$cid}] is resumed" . PHP_EOL;
}
echo "main coroutine" . PHP_EOL;
$cid1 = Study\Coroutine::create('task', 'a');
echo "main coroutine" . PHP_EOL;
$cid2 = Study\Coroutine::create('task', 'b');
echo "main coroutine" . PHP_EOL;
if (Study\Coroutine::isExist($cid1))
{
echo "coroutine [{$cid1}] is existent\n";
}
else
{
echo "coroutine [{$cid1}] is non-existent\n";
}
if (Study\Coroutine::isExist($cid2))
{
echo "coroutine [{$cid2}] is existent\n";
}
else
{
echo "coroutine [{$cid2}] is non-existent\n";
}
Study\Coroutine::resume($cid1);
echo "main coroutine" . PHP_EOL;
if (Study\Coroutine::isExist($cid1))
{
echo "coroutine [{$cid1}] is existent\n";
}
else
{
echo "coroutine [{$cid1}] is non-existent\n";
}
if (Study\Coroutine::isExist($cid2))
{
echo "coroutine [{$cid2}] is existent\n";
}
else
{
echo "coroutine [{$cid2}] is non-existent\n";
}
Study\Coroutine::resume($cid2);
echo "main coroutine" . PHP_EOL;
if (Study\Coroutine::isExist($cid1))
{
echo "coroutine [{$cid1}] is existent\n";
}
else
{
echo "coroutine [{$cid1}] is non-existent\n";
}
if (Study\Coroutine::isExist($cid2))
{
echo "coroutine [{$cid2}] is existent\n";
}
else
{
echo "coroutine [{$cid2}] is non-existent\n";
}然后编译、安装扩展：
~/codeDir/cppCode/study # make clean && make && make install
----------------------------------------------------------------------
Build complete.
Don't forget to run 'make test'.
Installing shared extensions: /usr/local/lib/php/extensions/no-debug-non-zts-20180731/
Installing header files: /usr/local/include/php/然后执行脚本：
~/codeDir/cppCode/study # php test.php
main coroutine
coroutine [1] create
main coroutine
coroutine [2] create
main coroutine
coroutine [1] is existent
coroutine [2] is existent
coroutine [1] is resumed
main coroutine
coroutine [1] is non-existent
coroutine [2] is existent
coroutine [2] is resumed
main coroutine
coroutine [1] is non-existent
coroutine [2] is non-existent
~/codeDir/cppCode/study # 符合预期。