how ot use json in php code example

Example 1: how to receive json data in php

$data = json_decode(file_get_contents('php://input'), true);
print_r($data);
echo $data;

Example 2: return json in php

//code igniter
$query="qry";
$query = $this->db->query($query);
$res=$query->result();
return json_encode($res);