Implementation of PayPal EWP in PHP

I'm new to the integration of PayPal in PHP.

I found some tutorial and I followed it.Now, I'm having problems with sandbox:

The email address for the business is not present in the encrypted blob. Please contact your merchant.

I have tried sending e-mail and Merchant ID of my Sandbox account, but no luck.

My code:

define("SANDBOX", 1);$business_id="paypal@***********";if(SANDBOX) $business_id="***********";

The data to be encrypted:

$form = array('cmd' => '_s-xclick','cert_id' => '*************','business' => $business_id,'custom' => 'test',        //'invoice' => '...','currency_code' => 'EUR','no_shipping' => '1','item_name' => 'TestItem','item_number' => '12345','amount' => '10'    );$encrypted = paypal_encrypt($form);function paypal_encrypt($hash){    ...trimmed...    $data = "";    foreach ($hash as $key => $value) {        if ($value != "") {            //echo "Adding to blob: $key=$value\n";            $data .= "$key=$value\n";        }    }    $openssl_cmd = "($OPENSSL smime -sign -signer $MY_CERT_FILE -inkey $MY_KEY_FILE " ."-outform der -nodetach -binary <<_EOF_\n$data\n_EOF_\n) | " ."$OPENSSL smime -encrypt -des3 -binary -outform pem $PAYPAL_CERT_FILE";    exec($openssl_cmd, $output, $error);    ...trimmed...};?> 

The PayPal form is:

<form action="https://<?php if(SANDBOX) echo "www.sandbox"; else echo "www"; ?>.paypal.com/cgi-bin/webscr" method="post" target=_blank><input type="hidden" name="cmd" value="_s-xclick"><input type="hidden" name="encrypted" value="<?php echo $encrypted; ?>"><input type="submit" value="Pay"></form>

The code is just a sample from the tutorial, I haven't edited it too much.