I am trying to send bitcoin implementing blockcypher API having difficulty in using the following code snippet...

i. http://blockcypher.github.io/php-client/sample/doc/transaction-api/CreateTransaction.html
ii. http://blockcypher.github.io/php-client/sample/doc/transaction-api/CreateAndSignAndSendTransaction.html

The transaction is being perfectly created, but following error is being thrown while trying to send it...

Catchable fatal error: Argument 1 passed to BlockCypher\Crypto\PrivateKeyList::addPrivateKey() must be an instance of BitWasp\Bitcoin\Key\PrivateKeyInterface, instance of BitWasp\Bitcoin\Crypto\EcAdapter\Impl\PhpEcc\Key\PrivateKey given, called in /www/myserver.com/blockcypher/lib/BlockCypher/Crypto/PrivateKeyList.php on line 42 and defined in /www/myserver.com/blockcypher/lib/BlockCypher/Crypto/PrivateKeyList.php on line 53

How do I solve this ?