一直试图获取SCOPE_IDENTITY（）（最后一个插入到DB中的ID）并将其作为变量存储在我的PHP函数中。

这是我目前拥有的：

// Confirm booking (update database) function
public function insert_userPost($conn) 
{
    // SQL INSERT command
    $sql = ("
           INSERT INTO userPost (content, submitted, emotion)
           VALUES ('$this->post', 'NOW()', '$this->emotion');
           ");
    if ($conn->query($sql) === TRUE) 
    {
        //echo "success";
        $sql = ("SELECT SCOPE_IDENTITY() as Id");
        $result = $conn->query($sql);
        echo $result;
        //header('Location: feed.php?filter=all&page=1');
    } 
    else 
    {
        echo "Error: " . $sql . "<br>" . $conn->error;
    }
}

我做错了什么？

编辑：

另外…在构造中，我试图在$ this-> post中传递ID（$ this-> Id），但它返回0。我可以看到这是由于我只设置了$查询通过后this->
Id，因此返回0，但我不确定如何继续。有什么建议？

// Construct
public function __construct($content, $emotion, $conn)
{
    $this->content = $content;
    $this->emotion = $emotion;
    $this->post = 
        "<div id=\'post\'>
            <div id=\'postContent\'>
                <p><b>I\'m $this->emotion because</b> $this->Id $this->content<span class=\'emot\'id=\'$this->emotion\'></span></p>
            </div>
            <div id=\'postInfo\'>
                <span class=\'postRelate\' title=\'Click to relate +1\'><p><b>relate</b> (0)</p></span>
                <span class=\'postSubmitted\'><p>submitted X minutes ago</p></span>
            </div>
        </div>";     
}

// Confirm booking (update database) function
public function insert_userPost($conn) 
{
    // SQL INSERT command
    $sql = ("INSERT INTO userPost (content, submitted, emotion)
             VALUES ('$this->post', NOW(), '$this->emotion')");
    if ($conn->query($sql) === TRUE) 
    {
        //echo "success";
        echo $this->Id = $conn->insert_id;
        //header('Location: feed.php?filter=all&page=1');
    } 
    else 
    {
        echo "Error: " . $sql . "<br>" . $conn->error;
    }
}