php - 致命错误：未捕获的类型错误：mysqli_num_rows()：参数 #1 ($result) 必须是 mysqli_result 类型，

Question

在我的 registration.php 表单中编写“已发送电子邮件”代码时弹出错误错误的完整标题：

致命错误：未捕获的类型错误：mysqli_num_rows()：参数 #1 ($result) 必须是 mysqli_result 类型，C:\xampp\htdocs\prototype\registration.php:19 中给出的布尔型堆栈跟踪：#0 C:\xampp\ htdocs\prototype\registration.php(19):mysqli_num_rows(false) #1 {main} 在第 19 行的 C:\xampp\htdocs\prototype\registration.php 中抛出

代码：

<?php

session_start();


$con = mysqli_connect('localhost','sjahub','123456');

mysqli_select_db($con, 'userregistration');

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

$s = " select * from users where email = '$email'";

$result = mysqli_query($con, $s);

$num = mysqli_num_rows($result);

if ($num == 1){
    echo" Email Already Taken";
}else{
    $reg= " insert into usertable(name , grade , email , password) values ('$name' , '$grade' , 
'$email' , '$password')";
    mysqli_query($con, $reg);
    echo" Registration Successful!";
}

?>

标签： phphtmlmysqldatabase