To create a new flavor asset for an existing entry, call the flavorAsset.convert API action.

<?php require_once('lib/KalturaClient.php'); 
$config = new KalturaConfiguration($partnerId); 
$config->serviceUrl = 'https://www.kaltura.com/'; 
$client = new KalturaClient($config); 
$client->setKs('AddYourKS'); 
$entryId = '1_entryIdString'; 
$flavorParamsId = 11111; 
$results = $client->flavorAsset->convert($entryId, $flavorParamsId);