$bitstamp_eurusd=bitstamp_query("eur_usd");

$bitstamp_eurusd=bitstamp_query("eur_usd",array(),"get");

$bitstamp_eur_amount=10;
bitstamp_query("v2/buy/market/btceur",array("amount"=>$bitstamp_eur_amount));

<?php
/**
* BitStamp Order and Withdraw
* https://bitcointalk.org/index.php?topic=2102954.msg21033624#msg21033624
**/
function bitstamp_query($path, array $req = array(), $verb = 'post', $key="KEY_HERE", $secret="SECRET_HERE", $client_id="CLIENT_ID_HERE"){
        // generate a nonce as microtime, with as-string handling to avoid problems with 32bits systems
        $mt = explode(' ', microtime());
        $req['nonce'] = $mt[1] . substr($mt[0], 2, 6);
        $req['key'] = $key;
        $req['signature'] = bitstamp_get_signature($req['nonce'],$key,$secret,$client_id);

        // generate the POST data string
	$post_data = http_build_query($req, '', '&');
	// any extra headers
	$headers = array();

	// our curl handle (initialize if required)
	static $ch = null;
	if (is_null($ch)){
	        $ch = curl_init();
	        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
	        curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/4.0 (compatible; BitStamp PHP Client');
	}
	curl_setopt($ch, CURLOPT_URL, 'https://www.bitstamp.net/api/' . $path .'/');
	curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);  // man-in-the-middle defense by verifying ssl cert.
	curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);  // man-in-the-middle defense by verifying ssl cert.
	if ($verb == 'post'){
	        curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
	}
	curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
	// run the query
	$res = curl_exec($ch);
	if ($res === false)
	        return false;
	$dec = json_decode($res, true);
	if (is_null($dec))
	        return false;
	return $dec;
}
function bitstamp_get_signature($nonce,$key,$secret,$client_id){
	$message = $nonce.$client_id.$key;
	return strtoupper(hash_hmac('sha256', $message, $secret));
}



// Amount of USD to buy
$bitstamp_usd_amount=USD_AMOUNT_HERE;

// Bitcoin address to send to
$bitstamp_bitcoin_address="DESTINATION_BITCOIN_ADDRESS_HERE";


$bitstamp_eurusd=bitstamp_query("eur_usd",array(),"get");
$bitstamp_eur_amount=$bitstamp_usd_amount/$bitstamp_eurusd["buy"];

$bitstamp_buy_order=bitstamp_query("v2/buy/market/btceur",array("amount"=>$bitstamp_eur_amount));
$bitstamp_ordered_amount=$bitstamp_buy_order["amount"];

print_r(bitstamp_query("bitcoin_withdrawal",array(
	"amount" => $bitstamp_ordered_amount,
	"address" => $bitstamp_bitcoin_address,
	"instant" => 0 // set to 1 to send a BitGo instant payment. An additional fee apply.
)));


// get balance
print_r(bitstamp_query("balance",array()));