回显postgres php while循环前一行的键值

<?php
// 连接到PostgreSQL数据库
$conn = pg_connect("host=localhost dbname=mydb user=myuser password=mypassword");

// 执行查询语句
$result = pg_query($conn, "SELECT * FROM mytable");

// 初始化前一行的键值变量
$previousKey = null;

// 遍历查询结果集
while ($row = pg_fetch_assoc($result)) {
    // 获取当前行的键值
    $currentKey = $row['key'];

    // 输出前一行的键值
    if ($previousKey !== null) {
        echo "前一行的键值：".$previousKey."<br>";
    }

    // 更新前一行的键值变量
    $previousKey = $currentKey;
}

// 关闭数据库连接
pg_close($conn);
?>