PDO postgresql最后插入id返回＆＃39; false＆＃39;或-1

Question

我有代码

$dbh = new PDO("pgsql:host=localhost; port=5432; dbname=gpd; user=postgres; password=postgres");
$sth = $dbh->prepare("INSERT INTO res (res_name, res_order) VALUES ('London', 1)");
$sth->execute();
$id = $dbh->lastInsertId();
echo $id;

记录插入，但$ id为空。

我尝试execure查询 INSERT INTO res (res_name, res_order) VALUES ('London', 1) RETURNING id

并收到一个值＆＃34; -1＆＃34;

Answer 1

回家后，我自己明白必须做什么

$dbh = new PDO("pgsql:host=localhost; port=5432; dbname=gpd; user=postgres; password=postgres");    
$sth = $dbh->prepare("INSERT INTO res (res_name, res_order) VALUES ('London', 1)");    
$sth->execute();    
$result = $sth->fetch(PDO::FETCH_ASSOC);    
echo "ID - ". $result["id"];

这很简单