how to r/w blob field in postgres

hi everyone

I have read the sample of create large object of pg_sql in the php manual.
here it is:

Example 1. Using Large Objects

1
2 <?php
3 $database = pg_Connect ("", "", "", "", "jacarta");
4 pg_exec ($database, "begin");
5 $oid = pg_locreate ($database);
6 echo ("$oid\n");
7 $handle = pg_loopen ($database, $oid, "w");
8 echo ("$handle\n");
9 pg_lowrite ($handle, "gaga");
10 pg_loclose ($handle);
11 pg_exec ($database, "commit");
12 ?>
13

I am confusing. According this sample, but which table and which record will be updated.
Anyone has tried this ? Please give me a full sample

thanks