Something like this do what you want?:
<?php
$key = '+Tir6+unMOaQ5tHqjjjwnlAMhccnCSMFEi3a0mhIxbW+O/GukjomGyzckQT2h0Ys70JezHbNq5YS3sYkNF29kCkz4HuNfy9eEjE/clA9/zyfT8ZcbnusLcLz2xNgbTp62fQdzBnReI5+dpj/N24krYvHaYIr8ACxDqBv2TR3E9M=AQAB';
include('Crypt/RSA.php');
$rsa = new Crypt_RSA();
$rsa->loadKey(array(
'e' => new Math_BigInteger(65537),
'n' => new Math_BigInteger(substr($key, 0, -4), -256)
));
$ciphertext = $rsa->encrypt('password');
echo bin2hex($ciphertext);
?>
This example uses phpseclib, a pure PHP RSA implementation. Although phpseclib does not support the format of the key you posted it does support raw public keys and as such converting to PKCS1 style keys is unnecessar. And the ciphertext's produced by phpseclib are perfectly interoperable with OpenSSL.