我试图在这个PHP代码中进行“用户采取”验证，它给了我这个错误：

Question

this is the code that i used:

<?php
$username = filter_input(INPUT_POST, 'username');
$password = filter_input(INPUT_POST, 'password');
if (!empty($username)){
if (!empty($password)){
$host = "localhost";
$dbusername = "root";
$dbpassword = "1234";
$dbname = "admin";

// Create connection
$conn = new mysqli ($host, $dbusername, $dbpassword, $dbname);


$dbunames = mysqli_query("SELECT * FROM entity WHERE username='$username'");



if (mysqli_num_rows($dbunames) > 0 ) { //check if there is already an entry 
for that username
    echo "Already taken";
  }



 else{
 $sql = "INSERT INTO entity (username, password)
 values ('$username','$password')";
 if ($conn->query($sql)){
  echo "New record is inserted sucessfully";
 }
 else{
  echo "Error: ". $sql ."
 ". $conn->error;
}
$conn->close();
}
}
else{
 echo "Password should not be empty";
die();
}
}
 else{
 echo "Username should not be empty";
 die();
 }


 ?>

and this is the error(in the web):

 Warning: mysqli_query() expects at least 2 parameters, 1 given in 
 C:\xampp\htdocs\form\connect.php on line 15

 Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null 
 given in C:\xampp\htdocs\form\connect.php on line 19
 New record is inserted sucessfully

i know "the record is inserted sucessfully" but the username is already taken validation is not working. i'm not good at php so i would be pleased if you tell me how to fix this code simply.

please help me!!!

Answer 1

$dbunames = mysqli_query("SELECT * FROM entity WHERE username='$username'");

needs to use the $conn variable like so:

$dbunames = mysqli_query($conn, "SELECT * FROM entity WHERE username='$username'");