PHP 不检查 MySQL 数据库中是否已有记录

Question

我有一个问题，所以如果用户偶然搜索并且它的代码不再激活，我想这样做。这样我就做了一个简单的代码:

$loginu = $_SESSION['login'];
$query = "SELECT `usrlogin`,`idcode` FROM `aktywacja` WHERE idcode = $numer AND usrlogin = $loginu ";
$result2 = mysql_query($query);
echo mysql_error();
if (mysql_num_rows($result2) == 0) {
    not found
}
else {
    found
}

并使我因以下错误而崩溃

Unknown column 'Kamil' in 'where clause' Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\kod.php on line 56 Where in this case I made a mistake?

请帮忙，

问候。

Answer 1

如果这些字符串不是整数，请确保用引号引起来:

WHERE idcode = $numer AND usrlogin = '$loginu'

并确保此变量 $numer 确实已定义，因为在您的问题中没有定义它。

强制性说明:

Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn about prepared statements instead, and use PDO or MySQLi - this article will help you decide which. If you choose PDO, here is a good tutorial.

下面是在 mysqli 中使用准备好的语句时的样子:

$loginu = $_SESSION['login'];
$numer = // make sure this is defined!    

$db = new mysqli('localhost', 'username', 'password', 'database_name');

$query = "SELECT `usrlogin`,`idcode` FROM `aktywacja` WHERE idcode = ? AND usrlogin = ?";
$select = $db->prepare($query);
// binding them
$select->bind_param('is', $numer, $loginu);
$select->execute();

if($select->num_rows > 0) {
    // found
} else {
    // not found
}