<?php
$host="XXX"; //replace with database hostname
$username="YYY"; //replace with database username
$password="ZZZ"; //replace with database password
$db_name="ZZZ"; //replace with database name

$ageFrom = $_GET['ageSearchFrom'];
$ageTo = $_GET['ageSearchTo'];

$con=mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

$sql = "SELECT * FROM users WHERE age BETWEEN '$ageFrom' AND '$ageTo'";

$result = mysql_query($sql);
$json = array();

if(mysql_num_rows($result)){
while($row=mysql_fetch_assoc($result)){
$json['user'][]=$row;
}
}
mysql_close($con);
echo json_encode($json);
?>