dialogflow-api-integration.php

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

$body = file_get_contents("php://input");
$bodyjson = json_decode($body);

$number1  = $bodyjson->queryResult->parameters->number1;
$number2  = $bodyjson->queryResult->parameters->number2;
$action   = $bodyjson->queryResult->action;
$result   = 0;

switch ($action) {
    case 'somar': 
         $result = $number1 + $number2; 
         break;
    case 'subtrair':
         $result = $number1 - $number2;
         break;
    case 'dividir':
        $result = $number1 / $number2;
        break;
    case 'multiplicar':
        $result = $number1 * $number2;
        break;
}

$response = [
    'fulfillmentText' => $result
];

$json = json_encode($response);

echo $json;