While loging in i am trying to validate values from 3 tables, but not working?

Question

i am getting these errors:

Warning: mysql_query() expects parameter 1 to be string, object given in H:\xamp\htdocs\newlogintry.php on line 12

Warning: mysql_query() expects parameter 1 to be string, object given in H:\xamp\htdocs\newlogintry.php on line 13

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in H:\xamp\htdocs\newlogintry.php on line 18

but this is the php code I wrote for it, I want to check whether the "type" of account is either teacher account or is it a pupil account if any among them then pass to main page with respective type parameter, please tell me if my usage of php is right since i am new to it, here is the php code(newlogintry.php)

<?php
$start=1;
$username=$_GET['username'];
$password=$_GET['password'];

$con=mysqli_connect("localhost","root","","repute system");
    if(mysqli_connect_errno()){
        echo "ERROR ".mysqli_connect_error();
    } 
        //$result = mysqli_query($con,"SELECT password FROM accounts WHERE username=".$username);
    $result = mysqli_query($con,"SELECT password,username,type,u_name FROM accounts ");
    $new = mysql_query($con, "SELECT name,USN,repute,acc_type,u_name FROM pupil ");
    $new1= mysql_query($con,"SELECT name,id,repute,acc_type,u_name FROM teacher");    
     
        

        
      if(mysqli_num_rows($new)>0)
        {
         while($row = mysqli_fetch_assoc($new)) {
                
                $pupilaccount = $row['acc_type'];       
         

                if(mysqli_num_rows($new1)>0)
                 {
                       while($row = mysqli_fetch_assoc($new1)) {
                           $teacheraccount = $row['acc_type'];
                          

                            if(mysqli_num_rows($result)>0)
                             {
                                  while($row = mysqli_fetch_assoc($result)) {
        
       
                                        $pass=$row['password'];
                                        $use=$row['username'];
                                        $type=$row['type'];

                                        if( $type==$teacheraccount and $password == $pass and $username==$use){
                                                 header("location:http://localhost/index.php?param=$teacheraccount&param1=$username");  
                                          exit();
                                      }
                                      else if($type==$pupilaccount and $password == $pass and $username==$use)
                                      {
                                            header("location:http://localhost/index.php?param==$pupilaccount&param1=$username");   
                                            exit();   
                                      }
                                  }
                            }         
             }
        }
      }              
        
        
          
        }
      }




?>

Answer 1

Error message:

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in H:\xamp\htdocs\newlogintry.php on line 31

Line 31 is:

                          if(mysqli_num_rows($result)>0)

This error means $result is not a mysqli_result which is what mysqli_num_rows expects, $result is most likely false which means the corresponding query failed.

$result is defined here:

  $result = mysqli_query($con,"SELECT password,username,type,u_name FROM accounts ");

You need to check if the query succeeded and if not, look for the error message. I recommend reading the manual on MySQLi at php.net.