The Google Translate API is a great option if you need to programmatically translate some text from one language to another.
Here is a sample PHP script that uses Curl to make a request to the Google Translate API. It sends the text "Hello, World!" in English and returns "¡Hola Mundo!" in Spanish.
<?php
/* Your Google API key */
$apiKey = 'xxxxxxxxxxxxxxxxxxx';
/* the text to translate */
$text = 'Hello, World!';
/* url to translate the text from English (en) to Spanish (es) */
$url = 'https://www.googleapis.com/language/translate/v2?key=' .
$apiKey . '&q=' . rawurlencode($text) .
'&source=en&target=es';
/* curl request */
$handle = curl_init($url);
curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($handle);
$responseDecoded = json_decode($response, true);
curl_close($handle);
/* the translated text ¡Hola Mundo! */
echo $responseDecoded['data']['translations'][0]['translatedText'];
?>
To use this sample script, all you really need is a Google API key.