return json in php

//Json Encode

$person = array( 
    "name" => "KINGASV", 
    "title" => "CTO"
); 
$personJSON=json_encode($person);//returns JSON string

//Json Decode

$personJSON = '{"name":"KINGASV","title":"CTO"}';

$person = json_decode($personJSON);

echo $person->name; // KINGASV

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

header('Content-type: application/json');
echo json_encode($array);

header('Content-Type: application/json'); 

$colors = array("red","blue","green");
echo json_encode($colors);