Question

我有这个代码块，应该用于在登录时验证用户。如果我尝试提供数据库中存在的电子邮件地址和密码，我会在$ loginerror中收到错误消息。我没有得到任何错误，但我的代码似乎没有得到任何结果集，因为当我尝试回显$stmt->num_rows时它打印出来0.请问我做错了什么？

这是代码块：

<?php

if(isset($_POST['signin'])){
    require_once "logincheck.php";

    $signin_email=$_POST['signin_email'];
    $signin_password=$_POST['signin_password'];

if($valid){
        require_once 'scripts/connect_to_mysql.php';     

        $sql ="SELECT First_name, Last_name FROM customer WHERE Email=? AND Password=?";
        $stmt=$conn->prepare($sql);//preparing the statement
        if(!$stmt){
            echo "Unable to prepare: ".$conn->errno. " " .$conn->error;
        }
        //executing the statement
        //$date=date('d m Y h:i:s');
        if(!$stmt->bind_param('ss', $signin_email, $signin_password)){//bind parameters to sql statement. i=integer, s=string, b=blob, d=double 
            echo "Binding parameters failed: ".$stmt->errno. " " . $stmt->error;
        }
        if(!$stmt->execute()){//executing the statement
            echo "Statement Execution failed: ". $stmt->error;
        }
        if(!$stmt->bind_result($firstname,$lastname)){// used to bind variables to a prepared statement for result storage
            echo "Unable to bind results to variables: ".$stmt->error;
        }
        //echo $stmt->num_rows;
        if($stmt->num_rows===1){//to check if username and password actually exists
        while($stmt->fetch()){
            $user=$firstname. " ". $lastname;
            echo $user;
        }
        $_SESSION['user']=$user;
        header('location:logintest.php');
        exit();
        }
        else{

            $loginerror= "Invalid Email address/Password. Please try again";
        }
        $stmt->close();//closing the prepared statement
        $conn->close();//closing the connection

}

}
?>

Answer 1

好的，我可以通过在代码中添加$stmt->store_result()来解决这个问题。所以现在我有，

if(!$stmt->bind_result($firstname,$lastname)){// used to bind variables to a prepared statement for result storage
            echo "Unable to bind results to variables: ".$stmt->error;
        }

        $stmt->store_result();

        if($stmt->num_rows===1){//to check if username and password actually exists
        while($stmt->fetch()){
            $user=$firstname. " ". $lastname;
            echo $user;
        }

取代：

if(!$stmt->bind_result($firstname,$lastname)){// used to bind variables to a prepared statement for result storage
                echo "Unable to bind results to variables: ".$stmt->error;
            }

            if($stmt->num_rows===1){//to check if username and password actually exists
            while($stmt->fetch()){
                $user=$firstname. " ". $lastname;
                echo $user;
            }

根据PHP Manual here，您需要为store_result()添加num_rows才能让{{1}}工作。

Answer 2

如果您使用的是MySQL，PDOStatement :: rowCount（）将返回结果集中的行数。

对于其他数据库/ MySQL，您可以

$rows = $stmt->fetchAll(); 
$rowCount = count($rows);

无法从数据库中检索数据。行数= 0

2 个答案: