PHP why I only can insert 1 single data into my database(mysql)

Question

I can only insert one single data into my database after that I refresh and try to insert another data it will only show 'Unable to register! Please Try Again!' below is my code what's the problem? :

<?php
include "conn.php"; // connection
$username = $_POST['user']; 
$password = $_POST['pass'];
$confirmpassword = $_POST['confirmpass'];
$email = $_POST['email']; 


 if($password !== $confirmpassword) {   echo "<script>alert('Password and confirmed password not same!'); ";
 die("window.history.go(-1);</script>"); } 

//write the insert sql query
 $sql = "Insert into users (User_Name, User_Password, User_Email, User_Last_login ) VALUES ('$username','".md5($password)."','$email','".date("Y-m-d H:i:s")."');";

//to check the query executed or not
 mysqli_query($conn, $sql);

 if(mysqli_affected_rows($conn) <=0) 
 {   
    die ("<script>alert('Unable to register! \\nPlease Try Again!');window.history.go(-1);</script>");
 }

 echo "<script>alert('Register Successfully!Please login now!');window.history.go(-1);</script>";
 echo "window.location.href='login.html';</script>";         
?>

I have try to solve this for few hours tried solution from other question but still not working, I still only can insert 1 data after that it keep shows Unable to register! Please Try Again!

Answer 1

i think that :

if(mysqli_affected_rows($conn)<=0)

is the problem, because it returns the number of affected rows in the previous SELECT, INSERT, UPDATE, REPLACE, or DELETE query. after the first insert, it will always be true.

what did you want to test??