This script runs daily and "Dollar Cost Average"-buys $40 BTC and $10 ETH per day

btc-eth-dca-buy.php

<?php

// Forked from @levelsio

function generateBitstampSignature( $nonce ) {
	$message = $nonce . BITSTAMP_ID . BITSTAMP_KEY;

	return strtoupper( hash_hmac( 'sha256', $message, BITSTAMP_SECRET ) );
}

function bitstamp_request( $url, $payload = array() ) {

	$mt     = explode( ' ', microtime() );
	$nonce  = $mt[1] . substr( $mt[0], 2, 6 );
	$fields = array_merge( $payload, array(
		'key'       => urlencode( BITSTAMP_KEY ),
		'signature' => urlencode( generateBitstampSignature( $nonce ) ),
		'nonce'     => urlencode( $nonce ),
	) );
	//url-ify the data for the POST
	$postdata = http_build_query( $fields );
	$opts = array(
		'http' =>
			array(
				'method'  => 'POST',
				'header'  => 'Content-type: application/x-www-form-urlencoded',
				'content' => $postdata
			)
	);

	$context = stream_context_create( $opts );
	$result = file_get_contents( $url, false, $context );
	return json_decode( $result, true );
}

//
$conf = Utils::getFirebaseData( 'btc/daily-buy' );
$text = "Bitcoin:";

foreach ( $conf as $ticker => $amount ){
	$amount = floatval( $amount );
	if ( $amount > 0 ) {
		$t = strtoupper( $ticker );
		// get price
		$url       = "https://www.bitstamp.net/api/v2/ticker/$ticker";
		$reply     = json_decode( file_get_contents( $url ), true );
		$btc_price = $reply['ask'];
		Utils::log( LOG_INFO, "$t Price: " . $btc_price );
		// if BTC price outlier, exit
		if ( $btc_price < 1000 || $btc_price > 100000 ) {
			Utils::log( LOG_WARNING, "Exiting because price either <1,000 or >100,000" );
			Utils::slack( "Bitcoin: Price out of parameter: $btc_price","Bitcoin" , "bitcoin" );
			exit;
		}
		$btcToBuy = round( $amount / $btc_price, 8 );
		$msg = "Buying " . $amount . " of $t, which equals " . $btcToBuy;
		Utils::log( LOG_INFO,$msg );
		$text .= "\n{$msg}: ";
		$result = bitstamp_request( "https://www.bitstamp.net/api/v2/buy/market/$ticker/", array( 'amount' => urlencode( $btcToBuy ) ) );
		if ( ! empty( $result['status'] ) && $result['status'] === 'error' ) {
			Utils::log( LOG_ERR, print_r( $result['reason'], true ) );
			$text .= "ERROR";
		} else {
			Utils::log( LOG_DEBUG, print_r( $result, true ) );
			$text .= "OK";
		}
	}
}

?>