Calls the System
IPC function semop to perform semaphore operations such as signaling and waiting.
OPSTRING must be a packed array of semop structures. Each semop structure can be generated with
pack("sss", $semnum, $semop, $semflag). The number of semaphore operations is implied by the length of
TRUE if successful, or
FALSE if there is an error. As an example, the following code waits on semaphore $semnum of semaphore id $semid: