Tie PHP Search with Form Options Selection

How can I integrate search results from as the example picture shows? Right now I have :

if(isset($_POST['q'])) {

$q = $_POST['q'];

$select = $db->query("SELECT * FROM customers WHERE FName LIKE '%$q%' OR 

LName LIKE '%$q%' ORDER BY ID DESC");

//Search Form Box
<form method="post">
<input type="text" name="q" /> <input type="submit" name="search" />
</form>

My desired end result is being able to type in a form search field, after the first 3 characters are typed, have the form be selectable and populate from my "items" database table, and be selectable. The I want to be able to dynamically add extra form fields(so the user can add items to an invoice).

Autocomplete code :

'$(function() {
    var availableTags = [
      "ActionScript",
      "AppleScript",
      "Asp",
      "BASIC",
      "C",
      "C++",
      "Clojure",
      "COBOL",
      "ColdFusion",
      "Erlang",
      "Fortran",
      "Groovy",
      "Haskell",
      "Java",
      "JavaScript",
      "Lisp",
      "Perl",
      "PHP",
      "Python",
      "Ruby",
      "Scala",
      "Scheme"
    ];
    $( "#tags" ).autocomplete({
      source: availableTags
    });
  });'

I cannot see how autocomplete would work, with the limited tags code.