php - 尽管表在数据库中并且两者都是小写，但 pg_connect 关系不存在？

Question

这是数据库中的表定义，我可以使用 PG Admin 插入行没问题

CREATE TABLE contact
(
  id serial NOT NULL,
  user_name character varying(50) NOT NULL DEFAULT ''::character varying,
  first_name character varying(50),
  last_name character varying(50),
  address character varying(100),
  phone character varying(25),
  email character varying(50),
  CONSTRAINT contact_pkey PRIMARY KEY (id),
  CONSTRAINT contact_user_name_key UNIQUE (user_name)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE contact
  OWNER TO postgres;

我尝试与此连接，但它的始终关系 <<contact>> 不存在，我尝试使用其他表，结果相同，关系 <<contact>> 不存在

    $username = $_POST['user_name'];
    $firstname = $_POST['first_name'];
    $lastname = $_POST['last_name'];
    $address = $_POST['address'];
    $phone = $_POST['phone'];
    $email = $_POST['email'];

    $host = "host=127.0.0.1";
    $port = "port=5432";
    $dbname = "dbname=testdb";
    $credentials = "user=postgres password=postgres";
    $db = pg_connect( "$host $port $dbnam $credentials" );

    if(!$db) {
        printMessage ("Can't connect to the database");
        die();
    }

    $sql =<<<EOF
        INSERT INTO contact (user_name, first_name, last_name, address, phone, email)
        VALUES ('$username', '$firstname', '$lastname', '$address', '$phone', '$email' );

        INSERT INTO user_login (id, password)
        VALUES((SELECT id FROM contact where user_name = '$username'), '$password');
EOF;

    $ret = pg_query($db, $sql);
    if(!$ret){
        echo pg_last_error($db);
    } 
    else {
        printMessage("Registered successfully");
    }

    pg_close($db);

我正在使用 Bitnami