com_print_typeinfo is really useful if you're trying to figure out what properties and methods you have access to.  For example, I might do:

<?php
    $oExplorer = new COM("Shell.Application");
    com_print_typeinfo($oExplorer);
?>

The first line shows me the class of the object (what VBScript calls 'typename'), in my case IShellDispatch4.  It's frequently the case that if you plunk that in as the second argument to com_print_typeinfo, you get way more methods/properties coming back.  Thus:

<?php
    $oExplorer = new COM("Shell.Application");
    com_print_typeinfo($oExplorer, "IShellDispatch4");
?>

Furthermore, you might get additional functions listed if you try lower number suffixes (or not).  At any rate, it would be useful for PHP to have a typename function like VBScript does.  For example, if you iterate through the Windows of $oExplorer you get both IE and Explorer windows and typename is the easy way to differentiate between them.  Here's what I'm using:

<?php
    function typeName($objCOM) {
    if (empty($objCOM)) return "no COM object";
    if (gettype($objCOM)!="object") return "not a COM object";
    ob_start();
    com_print_typeinfo($objCOM);
    $typeInfo = ob_get_contents();
    ob_end_clean();
    $pattern = "/^\\s*class (.*) \\{/";
    if (!($matchCnt = preg_match($pattern, $typeInfo, $aMatch))) return "Not found";
    return $aMatch[1];
}
?>

Csaba Gabor from Vienna

In my particular version of PHP, the second and third arguments are not, in fact, optional.

Passing in '' for both, however, yielded a bucketful of information.

YMMV