PHP compiled without OpenSSL support? Here's how you can call the openssl command-line utility to achieve the same goal:

<?php
// $sealed and $env_key are assumed to contain the sealed data
// and our envelope key, both given to us by the sealer.

// specify private key file and passphrase
$pkey_file='key.pem';
$pkey_pp='netsvc';

// call openssl to decrypt envelope key
$ph=proc_open('openssl rsautl -decrypt -inkey '.
 escapeshellarg($pkey_file).' -passin fd:3',array(
  0 => array('pipe','r'), // stdin < envelope key
  1 => array('pipe','w'), // stdout > decoded envelope key
  2 => STDERR,
  3 => array('pipe','r'), // < passphrase
 ),$pipes);
// write envelope key
fwrite($pipes[0],$env_key);
fclose($pipes[0]);
// write private key passphrase
fwrite($pipes[3],$pkey_pp);
fclose($pipes[3]);
// read decoded key, convert to hexadecimal
$env_key='';
while(!feof($pipes[1])){
  $env_key.=sprintf("%02x",ord(fgetc($pipes[1])));
}
fclose($pipes[1]);
if($xc=proc_close($ph)){
  echo "Exit code: $xc\n";
}

// call openssl to decryp
$ph=proc_open('openssl rc4 -d -iv 0 -K '.$env_key,array(
  0 => array('pipe','r'), // stdin < sealed data
  1 => array('pipe','w'), // stdout > opened data
  2 => STDERR,
 ),$pipes);
// write sealed data
fwrite($pipes[0],$sealed);
fclose($pipes[0]);
// read opened data
//$open=stream_get_contents($pipes[1]);
$open='';
while(!feof($pipes[1])){
  $open.=fgets($pipes[1]);
}
fclose($pipes[1]);
if($xc=proc_close($ph)){
  echo "Exit code: $xc\n";
}

// display the decrypted data
echo $open;

?>

Example code, assume mycert.pem is a certificate containing both private and public key.

$cert = file_get_contents("mycert.pem");

$public = openssl_get_publickey($cert);
$private = openssl_get_privatekey($cert);

$data = "I'm a lumberjack and I'm okay.";

echo "Data before: {$data}\n";
openssl_seal($data, $cipher, $e, array($public));

echo "Ciphertext: {$cipher}\n";

openssl_open($cipher, $open, $e[0], $private);
echo "Decrypted: {$open}\n";