Unknown column '$foro' in 'where clause'

SELECT * FROM hv_foro_entrada WHERE foroid=$foro and es_tema=1 and confirmed=1 and id in (0) ORDER BY added desc LIMIT 0,20

Unknown column '$foro' in 'where clause'

SELECT COUNT(*) FROM hv_foro_entrada WHERE foroid=$foro and es_tema=1 and confirmed=1 and id in (0)