Autocomplete error

//Script::

<script>
$(function() {
$( "#tags" ).autocomplete({
source: "pAjax/search.php",
minLength: 1,
select: function( event, ui ) {
log( ui.item ?
"Selected: " + ui.item.value + " aka " + ui.item.id :
"Nothing selected, input was " + this.value );
}
});
});

</script>
//

//Search.php
$term = trim(strip_tags($_GET['term']));

$result= $crud->dkQuery("SELECT username, first_name, last_name  FROM tbl_user WHERE username LIKE '%{$term}%' limit 10");

 $row_set = array(); //u have to define the row_set array
 while ($row = mysql_fetch_array($result))
 {
     $row_set[]=htmlentities(stripslashes($row['first_name'])).' '.htmlentities(stripslashes($row['last_name']));
 }

 echo json_encode($row_set);


//But, ami kivabe aita akta valuer under a dekhabo? ami down arrow click korleo select korbe value, jemon tumi korecila... Code er kothay vul bujtecina... amar outpur dekhay but select korle value dekhay na input a....