pg_field_type_oid() returns an integer containing the OID of the base type of the given field_number in the given PostgreSQL result resource.
You can get more information about the field type by querying PostgreSQL's
pg_type system table using the OID obtained with this function.
The PostgreSQL format_type() function will convert a
type OID into an SQL standard type name.
If the field uses a PostgreSQL domain (rather than a basic type), it is the OID of the domain's underlying type that is returned, rather than the OID of the domain itself.
$dbconn = pg_connect("dbname=publisher") or die("Could not connect");
// Assume 'title' is a varchar type
$res = pg_query($dbconn, "select title from authors where author = 'Orwell'");
echo "Title field type OID: ", pg_field_type_oid($res, 0);
The above example will output:
Title field type OID: 1043