Just re-encountered this issue. If you have a table where there is an attribute of type varchar(2000) for instance (really just anything greater than 255), when you pull it out using sybase_connect, it will only return 255 characters. This is outlined as a bug on php.net. To get around this issue, use a convert to text or update the attribute to be of type text if you can.
select convert(text, reallybigvarcharattribute) from table
Written by Milton Lai