以前にも同じことでつまづいたような・・・ pdo sql

間違い
$sql=’update prof1 set k_number = k_number +1 where id = “$search_key” limit 1′;
$res = $dbh->query($sql);

正解
$sql=”update prof1 set k_number = k_number +1 where id = ‘$search_key’ limit 1″;
$res = $dbh->query($sql);