pg_lo_read_all

// remember, large objects must be obtained from within a transactionpg_query ($dbconn, "begin");// "assume" for this example that the large object resource number of the zipped file is "17899"$lo_oid = 17899;$handle_lo = pg_lo_open($dbconn,$lo_oid,"r") or die("<h1>Error.. can't get handle</h1>");//headers to send to the browser before beginning the binary downloadheader('Accept-Ranges: bytes');header('Content-Length: 32029974'); //this is the size of the zipped fileheader('Keep-Alive: timeout=15, max=100');header('Content-type: Application/x-zip');header('Content-Disposition: attachment; filename="superjob.zip"');pg_lo_read_all($handle_lo) or   die("<h1>Error, can't read large object.</h1>");// committing the data transactionpg_query ($dbconn, "commit");

Pay attention that if you omit the "length" parameter it will read a 8192 bytes object regardless to its real dimensions. If you want to use this function think to save the object size somewhere (usually a field in its table) before reading the object. Alternatively use the pg_lo_readall function.