(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)
openssl_pkcs7_decrypt — Decrypts an S/MIME encrypted message
$input_filename,$output_filename,$certificate,$private_key = null
   Decrypts the S/MIME encrypted message contained in the file specified by
   input_filename using the certificate and its
   associated private key specified by certificate and
   private_key.
  
input_filename
output_filename
       The decrypted message is written to the file specified by
       output_filename.
      
certificate
private_key
   Returns true on success or false on failure.
  
| Version | Description | 
|---|---|
| 8.0.0 | private_keyaccepts an OpenSSLAsymmetricKey
       or OpenSSLCertificate instance now;
       previously, a resource of typeOpenSSL keyorOpenSSL X.509 CSRwas accepted. | 
Example #1 openssl_pkcs7_decrypt() example
<?php
// $cert and $key are assumed to contain your personal certificate and private
// key pair, and that you are the recipient of an S/MIME message
$infilename = "encrypted.msg";  // this file holds your encrypted message
$outfilename = "decrypted.msg"; // make sure you can write to this file
if (openssl_pkcs7_decrypt($infilename, $outfilename, $cert, $key)) {
    echo "decrypted!";
} else {
    echo "failed to decrypt!";
}
?>