bool openssl_pkcs7_encrypt ( string $infile , string $outfile , mixed $recipcerts , array $headers [, int $flags = 0 [, int $cipherid = OPENSSL_CIPHER_RC2_40 ]] )
openssl_pkcs7_encrypt() takes the contents of the file named infile and encrypts them using an RC2 40-bit cipher so that they can only be read by the intended recipients specified by recipcerts.
Returns TRUE on success or FALSE on failure.