<?php

$host = 'localhost';
$db   = 'mydb';
$user = 'myuser';
$pass = 'mypass';
$charset = 'utf8';

$dsn = "mysql:host=$host;dbname=$db;charset=$charset";
$opt = [
PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
PDO::ATTR_EMULATE_PREPARES   => false,
];

$pdo = new PDO($dsn, $user, $pass, $opt);

$response = array();

$result = $pdo->query("SELECT * FROM c068t_k2_items where catid = 6");
$response["items"] = array();
while ($row = $result->fetch()) {
    //print_r($response);
$product = array();
    $product["id"] = $row["id"];
    $product["title"] = $row["title"];
    $product["catid"] = $row["catid"];
    $product["published"] = $row["published"];
    $product["introtext"] = $row["introtext"];
    array_push($response["items"], $product);
}
$response["success"] = 1;
echo json_encode($response);
?>

{
  "items": [
    {
      "id": 2,
      "title": "Заголовок",
      "catid": 6,
      "published": 1,
      "introtext": "Текст"
    },
    {
      "id": 2,
      "title": "Заголовок",
      "catid": 6,
      "published": 1,
      "introtext": "Текст"
    }
  ],
  "success": 1
}