//HTML
<div class="bs-example">
    	<input type="text" name="city" id="city" class="city tt-query" autocomplete="off" spellcheck="false" placeholder="Type your Query">
        <input type="text" name="typeahead" class="typeahead tt-query" autocomplete="off" spellcheck="false" placeholder="Type your Query">
    </div>

//JS
$(document).ready(function(){
var var1 = $('#city').val();
    $('input.typeahead').typeahead({
        name: 'typeahead',
        remote:'search.php?key=%QUERY&key2=var1',
        limit : 10
    });
});

//search.php
<?php
    $key=$_GET['key'];
	  $key2=$_GET['key2'];
    $array = array();
    $con=mysql_connect("localhost","root","");
    $db=mysql_select_db("newbach",$con);
    $query=mysql_query("select * from bk_area where city_id = '$key2' && area_name LIKE '%{$key}%'");
    while($row=mysql_fetch_assoc($query))
    {
      $array[] = $row['area_name'];
    }
    echo json_encode($array);
?>