shmop_write() will write a
string into shared memory block.
shmop_write() takes 3
parameters: shmid, which is the shared memory block
identifier created by shmop_open(), data, a string that
you want to write into shared memory block and offset, which
specifies where to start writing data inside the shared
memory segment.
This example will write data inside
$my_string into shared memory block, $shm_bytes_written will contain the number of
bytes written.