php - PHP和MySQL-mysqli_free_result()期望参数1为mysqli_result，在第110行给出的 bool 值

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Warning: mysql_fetch_* expects parameter 1 to be resource, boolean given error
110号线是mysqli_free_result($r);有人能解释一下我在这里做错了什么，我该怎么解决？
这是密码的一部分。

if(isset($user_pass) && ($user_pass == TRUE) && !empty($salt)) {
    $q = "SELECT users.user_id, users.first_name, users.user_level FROM users JOIN contact_info ON contact_info.user_id = users.user_id WHERE (contact_info.email = '" . $e . "' OR users.username = '" . $e . "') AND users.password = '" . $sha512 . "' AND users.active IS NULL";        
    $r = mysqli_query ($dbc, $q) or trigger_error("Query: $q\n<br />MySQL Error: " . mysqli_error($dbc));

    while($row = mysqli_fetch_array($r)){
        $approved = $row['user_id'];
    }       

    if ((@mysqli_num_rows($r) == 1 && $approved == 2)) {

        $_SESSION = mysqli_fetch_array ($r, MYSQLI_ASSOC); 
        // check if user is logged in then update the old login date
        $u = "UPDATE users JOIN contact_info ON contact_info.user_id = users.user_id SET users.last_login = NOW(), users.deletion = 0, users.deletion_date = NULL WHERE (contact_info.email = '" . $e . "' OR users.username = '" . $e . "') AND users.password = '" . $sha512 . "' AND users.active IS NULL"; 
        // save the info to the database
        $r = mysqli_query ($dbc, $u);
        mysqli_free_result($r);
        mysqli_close($dbc);

        exit();

    } else {
        echo 'Error;
    }

} else {
    echo 'Error';
}

Answer 1

不确定像INSERT这样的查询是否返回false？？请纠正我，因为我确信这发生在以前的php/mysql中