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