PHP从PostgreSQL Query获取结果字符串

<?php
$host = "localhost";
$dbname = "mydb";
$user = "myuser";
$password = "mypassword";

try {
    $conn = new PDO("pgsql:host=$host;dbname=$dbname", $user, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $stmt = $conn->prepare("SELECT * FROM mytable");
    $stmt->execute();

    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);

    foreach ($result as $row) {
        echo $row['column_name'] . "\n";
    }
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

$conn = null;
?>