HTML表单似乎不张贴到PHP

大家好，感谢您的宝贵时间。

不管我做了多少研究，我都找不到一个已经讨论过的解决方案。

问题是提交按钮自动重定向，似乎没有发布表单。它一直工作，直到我从MySQL函数转换到MySQLi。除了网站的这一部分，其他一切都正常。

HTML表单(myaccount.inc.php):

<div id="change-password">
<form class="clearfix" action="" method="post">
        <div><span class="he1">Change Password</span></div>
        <div>
            <?php include_once 'controllers/accountController.php'; ?>
        </div>
        <div><label class="fieldlabel" for="password">Current Password:</label></div>
        <input type="password" name="password" id="password" size="23" /><br />
        <div><label class="fieldlabel" for="passwordnew1">New Password:</label></div>
        <input type="password" name="passwordnew1" id="passwordnew1" size="23" /><br />
        <div><label class="fieldlabel" for="passwordnew2">Confirm New Password:</label></div>
        <input type="password" name="passwordnew2" id="passwordnew2" size="23" /><br />
        <input type="submit" name="submit" value="Change Password" class="bt_changepass" />
</form>
</div>

然后，由于没有更好的术语，这个表单由一些PHP控制。

PHP (accountController.php):

// Checking whether the Password Change form has been submitted.
if(isset($_POST['submit'])=='Change Password')
{
echo "<br />";
// Get the data from the database.
$sql = $mysqli->query("SELECT * FROM ss_members WHERE usr = '".$_SESSION['usr']."' AND pass = '".md5($_POST['password'])."'");
$row = $sql->fetch_assoc();
// Will hold our errors
$err = array();
if($_POST['password'] == "" || $_POST['passwordnew1'] == "" || $_POST['passwordnew2'] == "")
{
    $err[] = 'All the fields must be filled in!';
}
if(!$row['pass'] == md5($_POST['password']) && $_POST['passwordnew1'] != "" && $_POST['passwordnew2'] != "")
{
    $err[] = 'Current password is not correct!';
}
if($_POST['passwordnew1'] <> $_POST['passwordnew2'])
{
    $err[] = 'New passwords do not match!';
}
if(!count($err))
{
    if($row['usr'])
    {
        // If everything is OK change password.
        $stmt = $mysqli->prepare("UPDATE ss_members SET pass = md5(?) WHERE usr = {$_SESSION['usr']}");
        $stmt->bind_param('s', $_POST['passwordnew1']);
        $stmt->execute();
        $stmt->close();
        echo "Password has been sucessfully updated!<br />";
    }
    else
    {
        $err[]='Something broke!';
    }
}
if($err)
{
    // Save the error messages in the session.
    foreach($err as $error)
    {
        echo $error . "<br />";
    }   
}
echo "<br />";
}