sem_remove
Description
bool sem_remove ( int sem_identifier)sem_remove() removes the semaphore sem_identifier if it has been created by sem_get(), otherwise generates a warning.
如果成功则返回 TRUE，失败则返回 FALSE。
After removing the semaphore, it is no more accessible.
See also: sem_get(), sem_release() and sem_acquire().
注: This function does not work on Windows systems. It was added on PHP 4.1.0.