php - 在 PHP 表中查找空值

Question

此代码用于检查行中用户名 = 某些内容的值

$stmt1 = $conn->prepare("SELECT likedOne FROM UserData WHERE username = ?");
$stmt1->bind_param('s',$username);
//$username = $_POST["username"];
$username ="jim";
$stmt1->execute();
$stmt1->store_result();

该语句会检查 Value 是否为空吗？

if ($stmt1 == ''){}

它不起作用。

Answer 1

试试这个

$stmt1->num_rows > 0

或

$res = $stmt1->fetch();

if( !empty( $res )
{

}

现在你的代码看起来像

$stmt1 = $conn->prepare("SELECT likedOne FROM UserData WHERE username = ?");
$username ="jim";
$stmt1->bind_param('s', $username);
$stmt1->execute();
$stmt1->store_result();

if($stmt1->num_rows > 0)
{
    //data retrive condition here
}