(PHP 4 >= 4.0.4, PHP 5)
openssl_sign — Generate signature
$data
   , string &$signature
   , mixed $priv_key_id
   [, int $signature_alg = OPENSSL_ALGO_SHA1
  ] )
   openssl_sign() computes a signature for the
   specified data by using SHA1 for hashing
   followed by encryption using the private key associated with
   priv_key_id. Note that the data itself is
   not encrypted.
  
data
signature
       If the call was successful the signature is returned in
       signature.
      
priv_key_id
signature_algFor more information see the list of Signature Algorithms.
   Returns TRUE on success or FALSE on failure.
  
| Version | Description | 
|---|---|
| 5.0.0 | The signature_algparameter was added. | 
Example #1 openssl_sign() example
<?php
// $data is assumed to contain the data to be signed
// fetch private key from file and ready it
$fp = fopen("/src/openssl-0.9.6/demos/sign/key.pem", "r");
$priv_key = fread($fp, 8192);
fclose($fp);
$pkeyid = openssl_get_privatekey($priv_key);
// compute signature
openssl_sign($data, $signature, $pkeyid);
// free the key from memory
openssl_free_key($pkeyid);
?>