无法识别$ _FILE文本字段名称索引

I am trying to store an image into an mysql database but in the ajax page $_FILE['textfield_Name']['temp_name'] is not recognizing it. Help me to solve this problem.

This is my file page code

 <form class="form-horizontal signUPForm" method="post" action="most_wanted_ajax.php">
  <label for="images">Upload Image</label>
   <input type="file"  name="images">
   <br>
 <button type="submit" id="add" value="Submit" >Add Most Wanted</button>

</form>

my jquery code is:

     $("#add").click(function (e){
         $.post($(".signUPForm").attr("action"),$(".signUPForm").serializeArray(),function(res){

                            if(res!=null){
                            alert("mosted wanted added");                          
                        }
                        else
                        {
                            alert("Somthing is fishy");

                        }


                });                      

                });

and here is my most_wanted_ajax.php code

<?php

if(getimagesize($_FILES['images']['tmp_name'])==FALSE)
{}
else
{
$image=addslashes($_FILES['images']['tmp_name']);
$image=  file_get_contents($image);
$image=  base64_encode($image);


$con=mysqli_connect("localhost","root","","ecopsweb");



$insertSQL="insert into most_wanted(images) values('".$image."')";
$rs=  mysqli_query($con, $insertSQL);

$id=  mysqli_insert_id($con);

header("location: missing_person_info.php");


}


?>

in the most_wanted_ajax.php page give two errors

Notice: Undefined index: images in C:\wamp\www\eCopsWeb\adminModule\most_wanted_ajax.php on line 3

Warning: getimagesize(): Filename cannot be empty in C:\wamp\www\eCopsWeb\adminModule\most_wanted_ajax.php on line 3

Add enctype="multipart/form-data"> to your form tag.This value is required when you are using forms that have a file upload control

It would be

<form class="form-horizontal signUPForm" method="post" action="most_wanted_ajax.php" `enctype="multipart/form-data"`>