Typecasting question

I am familiar with typecasting. Booleans, ints, strings, etc. However while using an extension, more specifically the OpenSSL extension I have come across a problem I am not entirely familiar with. I have an array that looks like...

array('config'             => 'config/openssl.cnf',
      'encrypt_key'        => true,
      'private_key_type'   => 'OPENSSL_KEYTYPE_RSA',
      'digest_algorithm'   => 'sha256',
      'private_key_bits'   => 512,
      'x509_extensions'    => 'usr_cert',
      'encrypt_key_cipher' => 'OPENSSL_CIPHER_3DES');

And according to the current OpenSSL documentation regarding the configuration constants (http://www.php.net/manual/en/openssl.ciphers.php) the array needs to have the 'private_key_type' and 'encrypt_key_cipher' elements as an INT value vs the string they are currently. Like so. array('private_key_type' => OPENSSL_KEYTYPE_RSA,

      'encrypt_key_cipher' => OPENSSL_CIPHER_3DES);

I have tried to perform typecasting these two elements as an int but because they are specific to the extension I am not certain how I should go about doing this. According to the source for php (the openssl.c) file is an internal attribute that I cannot find an integer value for to set it manually vs. using the pre-defined constant values mentioned in the docs.