Creating web services for Iphone or Android using PHP

Here is simple example to create web services

//get data from request

$id = $_REQUEST['id'];

// do whatever you need to using mysql query,for example get user having this id
$out = mysql_fetch_array("select * from users where id = '".$id."'");
//encode the output to json format

$send = json_encode($out);
// return the encoded 
echo $send;