ISSET Php mysql

Question

伙计们，每当我点击我的表单上的提交按钮而没有文本框中的任何数据时，就会说“回复”“你的用户名或电子邮件已被删除！”; 。尽管形式没有任何数据，它怎么还能通过呢？什么是最好的解释？

if(isset($_POST['username']) && isset($_POST['email']))
{
    $username = $_POST['username'];
    $email = $_POST['email'];

    $extract= mysql_query("SELECT * FROM users where username='$username'");

    $resultq = mysql_num_rows($extract);
    if($resultq > 0)
    {
       echo 'Either your username, or email is already taken!';
       return;
    }

}

请你坚持这条线12个小时，我似乎无法继续前进:(

Answer 1

isset对空字符串呈现true。它检查变量的存在。这是一个detailed explanation。

您应该使用if (trim($_POST['username']) != "")

Answer 2

if(isset($_POST['submit']))
{
    $username = $_POST['username'];
    $email = $_POST['email'];

    $extract= mysql_query("SELECT * FROM users where username='$username'");

    $resultq = mysql_num_rows($extract);
    if($resultq > 0)
    {
       echo 'Either your username, or email is already taken!';
       return;
    }

}

Answer 3

您还可以尝试!empty：

如果您想同时检查username或email already exist，还需要在email查询中查看select

    if(!empty($_POST['username']) && !empty($_POST['email']))
    {
        $username = $_POST['username'];
        $email = $_POST['email'];

        $extract= mysql_query("SELECT * FROM users where username='$username' OR email='$email'");

        $resultq = mysql_num_rows($extract);
        if($resultq > 0)
        {
           echo 'Either your username, or email is already taken!';
           return false;
        }
        else
        {
            echo 'Accept';
            return true;
        }
    }