php - how to pass hidden id using json in jquery ui autocomplete? -

perhaps duplicate,but can't found solution posted question.i use jquery ui auto complete search box. works fine problem want search using id.example:when user type paris,i try send city_id in mysql search. problem how pass hidden id json?
here code:

 <input type="text" name="grno" id="grno" class="input" title="<?php echo $lng['vldgrno'];?> 

jquery code:

<script>  $(function() { function split( val ) {   return val.split( /,\s*/ ); } function extractlast( term ) {   return split( term ).pop(); }  $( "#grno" )   // don't navigate away field on tab when selecting item   .bind( "keydown", function( event ) {     if ( event.keycode === $.ui.keycode.tab &&         $( ).data( "ui-autocomplete" ).menu.active ) {       event.preventdefault();     }   })   .autocomplete({     source: function( request, response ) {       $.getjson( "pages/search.php", {         term: extractlast( request.term )       }, response );     },     search: function() {       // custom minlength       var term = extractlast( this.value );       if ( term.length < 1 ) {         return false;       }     },     focus: function() {       // prevent value inserted on focus       return false;     },     select: function( event, ui ) {       var terms = split( this.value );       // remove current input       terms.pop();       // add selected item       terms.push( ui.item.value );       // add placeholder comma-and-space @ end       terms.push( "" );       this.value = terms.join( "," );       alert(data.id);       return false;     }   });   });   </script> 

autocomplete.php :

<?php   mysql_connect('localhost','root','');  mysql_select_db('school');  $return_arr = array();  $term = trim(strip_tags($_get['term']));//retrieve search term autocomplete sends  //create select query   $query = "select `grno`,`first_name`,`student_id` `tbl_student` `grno` '%".$term."%' or `first_name` '%".$term."%'";   // run query   $result = mysql_query ($query);   $array = array();  while($obj = mysql_fetch_array($result)){  $array['name'] = $obj['first_name']."(".$obj['grno'].")";  array_push($return_arr,$obj['first_name']."(".$obj['grno'].")");  }    $json = json_encode($return_arr);  echo $json;  ?> 

so.how pass student_id in autocomplete.php,like label , value.{label='xyz' value='1'}

in autocomplete.php replace code

array_push($return_arr,array("value"=>$obj['student_id'],"label"=>$obj['first_name']."(".$obj['grno'].")"));  

and in script change this

 terms.push( ui.item.label );  $( "#stud_id" ).val( ui.item.value ); 

hope,this find.