我正在写一个网站。但我一直有一个未知的错误。 它说：
“警告：mysqli_num_rows（）期望参数1为mysqli_result，在第29行的/ Applications / XAMPP / xamppfiles / htdocs / social business kopie / index.php中给出null”
我不知道我需要改变我的PHP代码，我只是一个初学者。请有人帮帮我吗？
第29行
的index.php：
<?php
$reg = @$_POST['reg'];<p>
//declaring variables to prevent errors
$fn = ""; //First Name
$ln = ""; //Last Name
$un = ""; //Username
$em = ""; //Email
$em2 = ""; //Email 2
$pswd = ""; //Password
$pswd2 = ""; // Password 2
$d = ""; // Sign up Date
$u_check = ""; // Check if username exists
//registration form
$fn = strip_tags(@$_POST['fname']);
$ln = strip_tags(@$_POST['lname']);
$un = strip_tags(@$_POST['username']);
$em = strip_tags(@$_POST['email']);
$em2 = strip_tags(@$_POST['email2']);
$pswd = strip_tags(@$_POST['password']);
$pswd2 = strip_tags(@$_POST['password2']);
$d = date("Y-m-d"); // Year - Month - Day
if ($reg) {
if ($em==$em2) {
// Check if user already exists
$u_check = mysql_query("SELECT username FROM users WHERE username='$un'");
// Count the amount of rows where username = $un
$check = mysqli_num_rows($u_check);
if ($check == 0) {
//check all of the fields have been filed in
if ($fn&&$ln&&$un&&$em&&$em2&&$pswd&&$pswd2) {
// check that passwords match
if ($pswd==$pswd2) {
// check the maximum length of username/first name/last name does not exceed 25 characters
if (strlen($un)>25||strlen($fn)>25||strlen($ln)>25) {
echo "The maximum limit for username/first name/last name is 25 characters!";
}
else
{
// check the maximum length of password does not exceed 25 characters and is not less than 5 characters
if (strlen($pswd)>30||strlen($pswd)<5) {
echo "Your password must be between 5 and 30 characters long!";
}
else
{
//encrypt password and password 2 using md5 before sending to database
$pswd = md5($pswd);
$pswd2 = md5($pswd2);
$query = mysql_query("INSERT INTO users VALUES ('','$un','$fn','$ln','$em','$pswd','$d','0')");
die("
Welcome to findFriends
Login to your account to get started ...");
}
}
}
else {
echo "Your passwords don't match!";
}
}
else
{
echo "Please fill in all of the fields";
}
}
else
{
echo "Username already taken ...";
}
}
else {
echo "Your E-mails don't match!";
}
}
?>