<input type="text" id="IDAlim">

<div class="col-md-6">
<section>
        <li id="demo"></li>
</section>
</div>

<script src="jsjquery.js"></script>
<script type="text/javascript">

var list = document.getElementById('demo');
$(document).ready(function()
{

putIn();
function putIn() {

    var focused = $(':focus');
    $("#IDAlim").focus();
    focused.focus();

    var IDAlim = document.getElementById('IDAlim').value;
    var quantite = "1";
    var entry = document.createElement('li');

    if(IDAlim != "")
    {
            $.post('validation.php',{IDAlim: $('#IDAlim').val()}, function(data){
                if(data.exists){
                    alert('Is in DB');
                    $("#demo").append('<li class="list-group-item">'+IDAlim+' '+quantite+'x'+'</li>');
                }else{
                    alert('Re-Scan please');
                }
             }, 'JSON');

        setTimeout(function(){ putIn() }, 800);
        $("#IDAlim").val('');
    }
    else
    {
        entry.appendChild(document.createTextNode(IDAlim));
        setTimeout(function(){ putIn() }, 800);
        $("#IDAlim").val('');
    }

}


})
</script>

<?php

//set the headers to be a json string
header('content-type: text/json');

//no need to continue if there is no value in the POST IDAlim
if(!isset($_POST['IDAlim']))
    echo json_encode(array('non' => 'POSTError'));



//Variable for db connection
$host="localhost";
$user="root";
$pass="";
$dbname="aliments";

try
  {
    $dbcon = new PDO("mysql:host={$host};dbname={$dbname}",$user,$pass, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

    $query = $dbcon->prepare('SELECT nom FROM tblaliments WHERE nom = :nomAlim');

    $query->bindParam(':nomAlim', $_POST['IDAlim']);

    $query->execute();

    //return the json object containing the result of if the IDAlim exists or not. The $.post in my jquery will access it.
echo json_encode(array('exists' => $query->rowCount()));
  }
  catch (Exception $e)
  {
    echo json_encode(array('non' => 'PDOError'));
  }
?>