See http://derickrethans.nl/translating-twitter-part2.html

bing-translate-nofgc.php

<?php

$apiBase = 'http://api.microsofttranslator.com/V2/Http.svc';
$appId   = 'yourappid';
$text    = 'Een hoge boom vangt veel wind';

$streamContext = stream_context_create(array('http' => array(
	'method'  => 'POST',
	'content' => '',
	'header'  => implode("\r\n", array('Content-Type: text/xml', 'Content-Length: 0')),
)));

libxml_set_streams_context($streamContext);

$bingResponse = simplexml_load_file(
	"{$apiBase}/GetTranslations?appId={$appId}&from=&to=en&maxTranslations=1&text=".urlencode($text)
);

$language  = (string) $bingResponse->From;
$inEnglish = (string) $bingResponse->Translations->TranslationMatch->TranslatedText;

var_dump( $language, $inEnglish );

bing-translate.php

<?php

$apiBase = 'http://api.microsofttranslator.com/V2/Http.svc';
$appId   = 'yourappid';
$text    = 'Een hoge boom vangt veel wind';

$streamContext = stream_context_create(array('http' => array(
	'method'  => 'POST',
	'content' => '',
	'header'  => implode("\r\n", array('Content-Type: text/xml', 'Content-Length: 0')),
)));

$bingResponse = simplexml_load_string(
        file_get_contents(
                "{$apiBase}/GetTranslations?appId={$appId}&from=&to=en&maxTranslations=1&text=".urlencode($text),
		false,
		$streamContext
        )
);

$language  = (string) $bingResponse->From;
$inEnglish = (string) $bingResponse->Translations->TranslationMatch->TranslatedText;

var_dump( $language, $inEnglish );