The S/MIME functions make use of flags which are specified using a bitfield which can include one or more of the following values:
| Constant | Description | 
|---|---|
| PKCS7_TEXT(int) | Adds text/plaincontent type headers to encrypted/signed
         message. If decrypting or verifying, it strips those headers from
         the output - if the decrypted or verified message is not of MIME typetext/plainthen an error will occur. | 
| PKCS7_BINARY(int) | Normally the input message is converted to "canonical" format
         which is effectively using CRandLFas end of line: as required by the S/MIME specification.  When this
          option is present, no translation occurs. This is useful when
          handling binary data which may not be in MIME format. | 
| PKCS7_NOINTERN(int) | When verifying a message, certificates (if
           any) included in the message are normally searched for the
           signing certificate. With this option only the
           certificates specified in the untrusted_certificates_filenameparameter of openssl_pkcs7_verify() are
           used.  The supplied certificates can still be used as
           untrusted CAs however. | 
| PKCS7_NOVERIFY(int) | Do not verify the signers certificate of a signed message. | 
| PKCS7_NOCHAIN(int) | Do not chain verification of signers certificates: that is don't use the certificates in the signed message as untrusted CAs. | 
| PKCS7_NOCERTS(int) | When signing a message the signer's certificate is normally
         included - with this option it is excluded.  This will reduce the
         size of the signed message but the verifier must have a copy of the
         signers certificate available locally (passed using the untrusted_certificates_filenameto
         openssl_pkcs7_verify() for example). | 
| PKCS7_NOATTR(int) | Normally when a message is signed, a set of attributes are included which include the signing time and the supported symmetric algorithms. With this option they are not included. | 
| PKCS7_DETACHED(int) | When signing a message, use cleartext signing with the MIME
         type "multipart/signed". This is the default
         if you do not specify anyflagsto
         openssl_pkcs7_sign().
         If you turn this option off, the message will be signed using
         opaque signing, which is more resistant to translation by mail relays
         but cannot be read by mail agents that do not support S/MIME. | 
| PKCS7_NOSIGS(int) | Don't try and verify the signatures on a message | 
| PKCS7_NOOLDMIMETYPE(int) | Available as of PHP 8.3.0.
          Sets the content-type to application/pkcs7-mimeinstead ofapplication/x-pkcs7-mimeto encrypt a message. | 
