undefined index error

html form
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<form onsubmit="return false"  class="form-horizontal" name="ads_post" id="post_form" enctype="multipart/form-data">
<div class="form-group">
      <label class="control-label col-sm-2" >Name</label>
      <div class="col-sm-10">
       <input type="text" class="form-control" id="name"  placeholder="Enter Name" name="user_name">

      </div>
      <span class="name_error"></span>
    </div>

<div class="form-group">
      <label class="control-label col-sm-2" >Image</label>
      <div class="col-sm-10">
      <table>
        <tr>
        <td><input type="file"  class="file" name="file" id="input-upload-img1"></td>

        </tr>
     </table>
      </div>
      <span class="img_error"></span>
    </div>
<div class="form-group">
                      <div class="col-sm-offset-2 col-sm-10">
                        <button type="submit" class="btn btn-primary" name="ad_submit">Submit</button>
                      </div>
                    </div>
</form>

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validate.js
--------------------------------------------------------------------------------------------------------
$(document).ready(function(){


     function verify_name(name){
    $(".name_error").hide();
    if(name == ""){
    $(".name_error").show();
    $(".name_error").html("plz provide your name");
    return false;
    }

   else{

    $(".name_error").show();
    $(".name_error").html("validating......");
    $.ajax({
    url:"classes/process.php",
    method:"post",
    data:{check_name:1,name:name},
    success:function(data){

    $(".name_error").show();
    if(data == "invalid_name"){
    $(".name_error").html("Plz provide valid name");
    return false;

    }
    else if(data == "good"){$(".name_error").html("ok");


    }
    },error: function(req, status, error) {
          // alert('Error: ' + req.status);
            console.log(error);
            console.log();
            }

    })
   }

}




   function verify_img(img){

    $(".img_error").hide();
    if(img == ""){
    $(".img_error").show();
    $(".img_error").html("plz Choose an image");
    return false;
    }
    else{
    $(".img_error").show();
    $(".img_error").html("validating....");
    $.ajax({

            url:"classes/process.php",
            type: "POST",
            data: {check_img:1,img:img},
            success: function(data)
            {

            $(".img_error").show();
    if (data=="size_large"){

    $(".img_error").html("image should be 1 mb");

    }
    else if(data=="invalid_format"){

    $(".img_error").html("only jpg,jpeg,png formates are allowed");

    }

    else{
    $(".img_error").html("ok");

    }



    },error: function(req, status, error) {
          // alert('Error: ' + req.status);
            console.log(error);
            console.log();
            }

     })
    }

}


$("#input-upload-img1").focusout(function(){
        var img=$("#input-upload-img1").val();
        verify_img(img);

          })



$("#name").focusout(function(){
    var name=$("#name").val();
    verify_name(name);

    })


    $("#post_form").on("submit",function(){

    var name = $("#name").val();

    var image = $("#input-upload-img1").val();

    if(name == ""){$(".name_error").show();
    $(".name_error").html("plz provide your name");
    return false;

    }


    else if(image == ""){$(".img_error").show();
    $(".img_error").html("plz select a image");
    return false;

    }

    else{

    $.ajax({
          url:"classes/process.php",
          method:"post",
          data:$("#post_form").serialize(),
          success:function(data){
          //if(data=="ok"){
          //window.location.href="index.php";
          alert(data);
          //}
          },error: function(req, status, error) {
          // alert('Error: ' + req.status);
            console.log(error);
            console.log();
            }

         })


    }
      })

})


---------------------------------------------------------------------------------------------------
process.php
---------------------------------------------------------------------------------------------------

<?php

include "dbcon.php";

class DataOperation extends database{

public function insert_image($table,$fields){

                     $name=$_FILES['file']['name'];
                     //$type=$_FILES['file']['type'];
                     //$extension=strtolower(substr($name,strpos($name,'.')+1));
                     //$size=$_FILES['file']['size'];
                     //$max_size=1000000;
                     $temp_name=$_FILES['file']['tmp_name'];
                     $location="../upload/";
                    if( move_uploaded_file($temp_name,$location.$name)){
                     $sql="";
                     $sql.="insert into ".$table ;
                     $sql.="(".implode(",",array_keys($fields)).") values ";
                     $sql.="(' ".implode(" ',' ",array_values($fields))." ' )";
                     $query=mysqli_query($this->con,$sql);
                     $img_id = mysqli_insert_id($this->con);
                     if ($query){
                                  return $img_id;
                             }
                    }
                    else
                    {
                      echo"something went wrong";
                    }
    }


    public function verify_name($name){
    //[email protected]
     $regexp = "/^[A-Za-z_]{2,5}$/";
     //if(!preg_match($regexp,$name)){
     //return "invalid_name";
     return (!preg_match($regexp,$name)) ? "invalid_name" : 'good';


    }

    public function verify_img($file){

    $extension=strtolower(substr($file,strpos($file,'.')+1));
    $size=$_FILES['file']['size'];
    $max_size=1000000;
    $type=$_FILES['file']['type'];
    if($extension=='jpg'||$extension=='jpeg'||$extension=='png'&& $type=='image/jpeg'&& $type=='image/jpg'&& $type=='image/png')
             {
                 if($size<=$max_size)
                 {
                    return "ok";
                 }

                 else{

                  return "size_large";
                 }
             }

    else {

      return "invalid_format";
    }
}





}

 $obj = new DataOperation;
 if(isset($_POST["check_name"])){
     $name=$_POST["name"];
     echo $data=$obj->verify_name($name);
     exit();
 }

 if(isset($_FILES['file']['check_img'])){
     $file=$_FILES['file']['img'];
     echo $data=$obj->verify_img($file);
     exit();
 }

 if(isset($_POST["user_name"])){



      $data=$obj->verify_name($_POST["user_name"]);
         if($data == "invalid_name"){
             echo "invalid name";
             exit();
            }else {
            $name= $_POST["user_name"];
        }


        $data=$obj->verify_img($_FILES['file']['name']);
         if($data == "invalid_extension"){
             echo "Only jpg,jpeg,and png files allowed";
             exit();
            }else {
            $file=$_FILES['file']['name'];
        }


        $ad_image = array(
                "img1" => $file,

                );
        $img_id = $obj->insert_image("img_upload",$ad_image);

        //user information
            $user_info = array(
                "name_user" => $name,

                );
                $id = $obj->insert_record("user",$user_info);

                $myarray=array(

                "user_id"=>$id,
                "img_id"=>$img_id,
                );

                if ($obj->insert_record("classified",$myarray)) {
                //header("location:../index.php?msg=Successfully inserted");
                echo "success";
                exit();
            }

        }

 ?>