pg_field_num() will return the number of the field number that corresponds to the field_name in the given PostgreSQL result resource.
This function used to be called pg_fieldnum().
$dbconn = pg_connect("dbname=publisher") or die("Could not connect");
$res = pg_query($dbconn, "select author, year, title from authors where author = 'Orwell'");
echo "Column 'title' is field number: ", pg_field_num($res, 'title');
The above example will output:
Column 'title' is field number: 2