PHP Manual . ... PHP 4 >= 4.0.6) openssl_pkcs7_encrypt -- Encrypt an S/MIME message . ... Be warned and use this function at your own risk. openssl_pkcs7_encrypt () takes the contents of the file named infilename and encrypts them using an RC2 40-bit cipher so that they can only be read by the intended recipients specified by recipcerts , which is either a lone X.509 certificate, or an array of X.509 certificates. headers is an array of headers that will be prepended to the ...