php - LAST_INSERT_ID() 无法使此代码工作

Question

我看不出我做错了什么，请帮忙。我正在学习 Select Last_Insert_Id，但我已经被困了几天了。

$result2 = $mysqli1->query("SELECT LAST_INSERT_ID()");

while($row = mysqli_fetch_assoc($result2)) {
    return $row;
}
$last_id = $row;

$sql = "UPDATE bao_admin_table SET Name='$name' WHERE ID = '$last_id' ";

if ( $mysqli1->query($sql)){

    $_SESSION['message'] = 'Registration successful!';
    header("location: success.php"); 

}else{
    $_SESSION['message'] = 'Registration failed!';
    header("location: error2.php");
}

Answer 1

我假设您可能正在插入录音，那么只有您才能获取最后插入的ID。有两种方法可以实现它，

1. 插入后获取最后插入的值。这就是你可以做到的

   $sql = "INSERT INTO MyGuests (firstname, lastname, email) VALUES ('John', 'Doe', 'john@example.com')";
   if (mysqli_query($conn, $sql)) 
   {
   $last_id = mysqli_insert_id($conn);
   echo "New record created successfully. Last inserted ID is: " . $last_id;
   } 
   else 
   {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
   }
   

2. 我希望您至少有主键从表中提取唯一记录，因此，这就是您如何通过按降序应用顺序来获取最后一个 id。

`

$sql = "SELECT * FROM MyGuests ORDER BY id DESC";
$result = $conn->query($sql);
if ($result->num_rows > 0) 
{// output data of each row
while($row = $result->fetch_assoc()) 
{
    echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} 
else 
{
echo "0 results";
}

`