准备好的语句检查行是否存在

Question

我是 PHP 中准备好的语句的新手，我想知道如何最好地检查一行是否已经存在，因为我在这个阶段似乎感到困惑：

<?php 
include '../config.php'; 

$stmt = $conn->prepare("INSERT INTO users (email, password) VALUES (?, ?)");
$stmt->bind_param("ss", $email, $password);

if(mysqli_num_rows($stmt) > 0) {
    $email = $_POST['email'];
    $password = $_POST['password'];
    $stmt->execute();
    header('Location: ../login.php');   
} else {
    echo 'user already exists';
}
$stmt->close();
$conn->close();
?>

上面返回else 语句，如果我切换它们，它将再次插入，使用else 语句并插入记录但仍然不检查。

** 更新 **

这是我的更新代码，您可以在下面获得帮助后查看..

<?php 
include '../config.php'; 

ini_set('display_errors', 1); ini_set('display_startup_errors', 1); error_reporting(E_ALL);

$email = $_POST['email'];
$password = $_POST['password'];

$stmt_check = $conn->prepare("SELECT * FROM users WHERE email =?");
$stmt_check->bind_param("s", $email);
$stmt_check->execute();
if($stmt_check->num_rows > 0) {
    echo 'user already exists';
} else {
    $stmt = $conn->prepare("INSERT INTO users (email, password) VALUES (?, ?)");
    $stmt->bind_param("ss", $email, $password);
    $stmt->execute();
    // header('Location: ../login.php');
}    
$stmt->close();
$conn->close();
?>

Answer 1

mysqli_num_rows 适用于 SELECT 语句。

$stmt_check = $conn->prepare("SELECT * FROM users WHERE email =? AND password =?");
$stmt_check->bind_param("ss", $email, $password);
$stmt_check->execute();
if(mysqli_num_rows($stmt_check) > 0)

更新代码

<?php 

include '../config.php'; 

$email = $_POST['email'];
$password = $_POST['password'];

$stmt_check = $conn->prepare("SELECT * FROM users WHERE email =? AND password =?");
$stmt_check->bind_param("ss", $email, $password);
$stmt_check->execute();
if($stmt_check->num_rows > 0){
  echo 'user already exists';
} else {
  $stmt = $conn->prepare("INSERT INTO users (email, password) VALUES (?, ?)");
  $stmt->bind_param("ss", $email, $password);
  $stmt->execute();
  header('Location: ../login.php');
}

$stmt->close();
$conn->close();
?>

快速链接

• mysqli_num_rows
• mysql_num_rows

哪些州，

此命令仅对像 SELECT 或 SHOW 这样的语句有效 返回一个实际的结果集。检索受影响的行数 通过 INSERT、UPDATE、REPLACE 或 DELETE 查询，使用 mysql_affected_rows().

编辑 1

改变

if(mysqli_num_rows($stmt_check) > 0){

到

if($stmt_check->num_rows > 0){

参见PHP mysqli_num_rows() Function

的Example2

Answer 2

这是我更新的代码，请尝试

  <?php 

include '../config.php'; 

$email = $_POST['email'];
$password = $_POST['password'];

$stmt_check = $conn->prepare("SELECT * FROM users WHERE email =? AND password =?");
$stmt_check->bind_param("ss", $email, $password);
$stmt_check->execute();
$stmt_check->store_result();
$numberofrows = $stmt_check->num_rows;

if(($numberofrows) > 0)
  echo 'user already exists';
} else {
  $stmt = $conn->prepare("INSERT INTO users (email, password) VALUES (?, ?)");
  $stmt->bind_param("ss", $email, $password);
  $stmt->execute();
  header('Location: ../login.php');
}

$stmt->close();
$conn->close();
?>

Answer 3

看看mysqli_stmt_affected_rows()

<?php include '../config.php'; 

$stmt = $conn->prepare("INSERT INTO users (email, password) VALUES (?, ?)");
$stmt->bind_param("ss", $_POST['email'], $_POST['password']);
$stmt->execute();

if(mysqli_stmt_affected_rows($stmt) > 0)
{
    header('Location: ../login.php');   
}
else
{
    echo 'user already exists';
}

$stmt->close();
$conn->close();
?>

Answer 4

<?php include '../config.php'; 

$stmt = $conn->prepare("INSERT INTO users (email, password) VALUES (?, ?)");
$stmt->bind_param("ss", $_POST['email'], $_POST['password']);
$result = $stmt->execute(); // this return a bool: true if row affected otherwise false

if($result)
{
    header('Location: ../login.php');   
}
else
{
    echo 'user already exists';
}

$stmt->close();
$conn->close();
?>