$s = $h->prepare(/select * from table where a = ?/);
  $s->execute($h->quote("myvalueforcolumna"));

##</code><code>##

  $s = $h->prepare(q/select * from table where a = / . $h->quote("myvalueforcolumna");

##</code><code>##

  select col1, col2, col3 from tab_name where (? is null or foo = ?) and (? is null or bar = ?) and (? is null or baz = ?)