This functionality seems to work fine in the 5.3.0 rc builds ( PHP 
5.3.0RC5-dev (cli) (built: Jun 27 2009 00:33:01) (DEBUG)).

The following script appears to work for me against most of the 
capicom.utilities functions: 

<?php 

try {
	$util = new COM('CAPICOM.Utilities.1');
} catch (Exception $e) {
	echo $e->getMessage() . "\n";
	echo 'exception initialising com object... terminating...';
}

$string = 'foo';

$encoded = $util->Base64Encode($string); /* encoded string is \r\n 
terminated */
echo $encoded . ' is base 64 encoded string:' . $util-
>Base64Decode($encoded) . "\n";
echo "\n\n";

$hex = $util->BinaryToHex($string);
echo "BinaryToHex: " . $util->BinaryToHex($string) . "\n";
echo "hextobinary: " . $util->HexToBinary($hex) . "\n";
define( 'CAPICOM_ENCODE_BASE64', 0 );

echo "Random Number: " . $util->GetRandom(10, CAPICOM_ENCODE_BASE64) . 
"\n";

$variant = $util->BinaryStringToByteArray($string);
$i = 0;
foreach( $variant as $v) {
 echo "Byte(" . $i++ . "): " . $v . "\n";
}


Outputing:
ZgBvAG8A
 is base 64 encoded string:foo

BinaryToHex: 66006F006F00
hextobinary: foo
Random Number: PiMSnPtckiHFCQ==

Byte(0): 102
Byte(1): 0
Byte(2): 111
Byte(3): 0
Byte(4): 111
Byte(5): 0

----------------------------------

1) It might be worth trying a newer version of php
2) it might be worth checking that the com object is registered 
correctly by attempting to access it from a vbscript

I was able to use CapiCom.Utilities.1 with PHP 5.2.11. Error is generated when capicom is not registered and class is not available on the machine.

Please let us know when Capicom is (or is not) available because I have a fresh XP 
install here, with a new PHP 5.3.2 install, and am also getting "Failed to create 
COM object 'CAPICOM.Utilities.1': Invalid syntax"

This is indeed because CAPICOM.Utilities.1 isn't installed.

What you need to do is to:
1) Install CAPICOM from: http://www.microsoft.com/downloads/details.aspx?FamilyId=860EE43A-A843-462F-ABB5-FF88EA5896F6&displaylang=en
2) Register the DLL: regsvr32 capicom.dll (capicom.dll is located in the installed folder in %ProgramFiles%)

Thanks for the replies/help on this. Is it possible to improve the error message 
so it says the COM object is "Not found" instead of "Invalid syntax"?

I understand if this is outside the control of PHP.