PHP - Php Insert Not Working

function insert(){
				$user = $_POST['user'];
				$pass = md5($_POST['pass']);
				$priv = "User";
				$mail = $_POST['mail'];
				$avatar = $_FILES['avatar']['name'];
				$date="now()";
				$submit = $_POST['submit'];
			
			
				$query = "INSERT INTO user(user,pass,priv,mail,avatar,date) VALUES(`$user`,`$pass`,`$priv`,`$mail`,`$avatar`,`$date`);";
				if($submit){
					$res = mysqli_query($con,$query) or die(mysqli_error($con));
				}
				
				
			}

//database
create table mydata (
	id int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
	fname varchar(20),	
    phoneno int(12) NOT NULL
    /*......*/
);
//class my data php

<?php

include('connect.php');
class InsertMydata {
    public function insertnow($fname, $phoneno) {
        $connect = new Connect;
        $insrt = $db -> prepare('INSERT INTO mydata (fname, phoneno) VALUES (?,?)');
		$insrt -> execute(array($fname, $phoneno));		
	}
}
?>


//insernow validate form

<?php
include('../classs/mydata.php');
//Declare data and error arrays
$errors = [];
$mydara = [];
if(!preg_match('/^[a-zA-Z]{4,15}$/', $_POST['fname'])) {
	$errors['fname'] = 'Enter full name!';
}
//this block not working even the phone exist
$connect = new Connect;
$phoneno = $_POST['phoneno'];
$checkiexist = $connect -> prepare('SELECT * FROM mydata WHERE phoneno = ?');
$checkiexist -> execute([$phoneno]);
if($checkiexist->rowCount() > 0) {
      $errors['phonenoexist'] = 'Try another phone number!';
 }
if(!empty($errors)){
      $data['success'] = false;
      $data['errors'] = $errors;
}else{
      $data['success'] = true;
      $data['message'] = 'success message!';  
      $mydata = new InsertMydata;
      $mydata -> insertnow($fname, $phoneno);
}
echo json_encode($data);

?>

//my ajax

$("#insertbtn").click( function(e) {
     var fname = $('#fname').val(),
         phoneno = $('#phoneno').val(),
           
       $.ajax({
           url: 'insertnow.php',
           type: 'POST',
           data: {fname:fname, phoneno:phoneno},
           dataType: "JSON",
           encode: true,
        }).done( function (data) {
         
         if (data.success == false) {
           if (data.errors.fname) {
                 $('#fname').append('<p class="text-danger">' + data.errors.fname + '</p>');
            } 
            if (data.errors.phonenoexist) {
              $('.card-header').append('<div class="alert alert-info alert-dismissible" role="alert">
                <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">×</span></button>'+data.errors.phonenoexist+'</div>');
            }
            } else {
             $('.card-header').append('<div class="alert alert-success alert-dismissible" role="alert"><button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">×</span></button>'+data.message+'</div>');
        }
    });
       e.preventDefault();
    });


//the problem is, the code insert data even if the phone exist why?

the problem is, the code insert data even if the phone exist why?

Hi, I have an app that access a MySQL database via a php script.
I noticed that INSERT was returning error but the data was being recorded successfully.
I finally traced the problem to be related with the line 
echo $conn->affected_rows;   

For some reason when it is an SQL INSERT it returns -11 but as I said the INSERTS executes successfully.

The app requesting the service sends in sequence:

char* txtSQL[]={"INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)",
                            "INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)",
                            "INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)",
                            "INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)",
                            "UPDATE activity set value=333 where value=130",
                            "SELECT sum(value) from activity where mac='a9c4952de6b4'",
                            "DELETE from activity WHERE value=333"};

I set a monitor to check what was being returned and got:

query=INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)
HttpResponse:  -   httpResponseCode: -11
query=INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)
HttpResponse:  -   httpResponseCode: -11
query=INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)
HttpResponse:  -   httpResponseCode: -11
query=INSERT INTO activity (mac,jd,date,time,area,type,value) VALUES ('a9c4952de6b4',2458454,'2018-12-01','10:22','Area0002','h',130)
HttpResponse:  -   httpResponseCode: -11
query=UPDATE activity set value=333 where value=130
HttpResponse: 4 *   httpResponseCode: 201   -------------------------------------->As can be seem the INSERTS above returned error but worked OK
query=SELECT sum(value) from activity where mac='a9c4952de6b4'
HttpResponse: 1379 *   httpResponseCode: 200
query=DELETE from activity WHERE value=333
HttpResponse: 4 *   httpResponseCode: 201

The  PHP script do ing the job i s as be low :

<?php
include('connection.php');

//these are just in case setting headers forcing it to always expire 
header('Cache-Control: no-cache, must-revalidate');

error_log(print_r($_POST,TRUE));

if( isset($_POST['query']) && isset($_POST['key']) ){                                   //checks if the tag post is there and if its been a proper form post
  header('Content-type: application/x-www-form-urlencoded');
  if($_POST['key']==$SQLKEY){                                                           //validates the SQL key
    $query=urldecode($_POST['query']);
    if(get_magic_quotes_gpc()){     //check if the worthless pile of crap magic quotes is enabled and if it is, strip the slashes from the query
      $query=stripslashes($query);
    }
    $conn = new mysqli($DB_ADDRESS,$DB_USER,$DB_PASS,$DB_NAME);    //connect

    if($conn->connect_error){                                                           //checks connection
      header("HTTP/1.0 400 Bad Request");
      echo "ERROR Database Connection Failed: " . $conn->connect_error, E_USER_ERROR;   //reports a DB connection failure
    } else {

      $result=$conn->query($query);                                                     //runs the posted query                        

      if($result === false){
        header("HTTP/1.0 400 Bad Request");                                             //sends back a bad request error
        echo "Wrong SQL: " . $query . " Error: " . $conn->error, E_USER_ERROR;          //errors if the query is bad and spits the error back to the client
      } else {
        if (strlen(stristr($query,"SELECT"))>0) {                                       //tests if it's a SELECT statement
          $csv = '';                                                                                // bug fix Undefined variable: csv
          while ($fieldinfo = $result->fetch_field()) {
            $csv .= $fieldinfo->name.",";
          }
          $csv = rtrim($csv, ",")."\n";
//********************************          echo $csv;                                                                    //prints header row
          $csv = '';

          $result->data_seek(0);
          while($row = $result->fetch_assoc()){
            foreach ($row as $key => $value) {
              $csv .= $value.",";
            }
            $csv = rtrim($csv, ",");                                                 //."\n";
          }
          echo $csv;                                                                    //prints all data rows
        } else {
          header("HTTP/1.0 201 Rows");
          echo $conn->affected_rows;       //if the query is anything but a SELECT, it will return the number of affected rows (INSERT IS  RETURNING -11)
        }
      }
      $conn->close();                                          //closes the DB
    }
  } else {
     header("HTTP/1.0 400 Bad Request");
     echo "-Bad Request";                                       //reports if the secret key was bad
  }
} else {
        header("HTTP/1.0 400 Bad Request");
        echo "*Bad Request";
}
?>

Any help will be much appreciated.
Thanks

Paulo Borges