如何使用PHP从数据库检查$username到UserName

Question

我正在使用PDO和PHP将信息写入数据库。我想检查$tblusername (这是用户输入的用户名)是否与我的数据库中username列中的任何内容相同。UserName在tblUsers下。下面是我的现有代码：

try {
        $tblusername = $_POST['Username'];
        $tblemail = $_POST['Email'];
        $tblpassword = $_POST['Password'];

        $conn = new PDO("mysql:host=$servername;dbname=mealplan", $username, $password);
        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $stmt = $conn->prepare("SELECT UserName FROM tblUsers");

        if($stmt->rowCount() > 0){
        die("Username already in use!");
        }else{
          echo "3";
          $sql = "INSERT INTO `tblUsers` (`UserName`, `Email`, `UserPassword`) VALUES ('?', '?', '?')";
          $stmt = $conn->prepare($sql)->execute([$tblusername, $tblemail, $tblpassword]);
        }

      } catch(PDOException $e) {
      echo "<style>.hidden { visibility: visible; } .shown { visibility: hidden; font-size: 0px }</style>";
      }
    }

任何帮助都将不胜感激！

Answer 1

在PHP中，您需要使用bindParam为where子句条件传递UserName参数，以便它有助于为给定的UserName提取唯一行。您可以遵循给定的代码。

$stmt = $conn->prepare("SELECT UserName FROM tblUsers where UserName=:tblusername");
$stmt->bindParam(':tblusername', $tblusername);   
$stmt->execute();

Answer 2

修好了！需要添加WHERE UserName = $tblUsername并删除'?‘并将其替换为？