Except you need this done in php. Well, I believe there is a way to call perl from php, though it may be a bit of a pain. (See also just plain google on that.) I would just do that. This html from regex stuff is such a pain that I would do that, call perl from php and use a module.

If it has to be regexes, no perl, post some sample input data so the monks can have a shot at it without having to create their own test data. Good luck!

I need to count the number of form fields in a string full of HTML. The problem is that this actually needs to be done in PHP, so no modules are allowed.

It's hard following you. Is your program perl, or PHP? If it's PHP, asking for help on a PHP site/newsgroup may bring better answers!
Anyway, what I understand is that you plan to use "perl compatible regexes" within PHP; but "perl compatible regexes" AREN'T perl. Regexes are a tiny part of perl really, and PHP so-called "compatible" implementation may vary considerably from the "Real Thing" (i.e. perl regexes). That's the first thing...

So I need a regular expression that counts all input elements

No, you probably don't. Parsing HTML with pure regexes is almost always a bad idea, unless you know precisely what limited HTML subset you'll actually have at input. Either you're working from within PHP, then you'll have to find some PHP module /library /tool /whatever to parse the HTML code, or you may call a perl program from your PHP code, and that perl program may use HTML::Parser or whatever perl module you may need.

I see that what you're really asking for is the regular expression(s) needed to do this task.

It would help if you posted your 'hideously ugly' regex code so that we could have a look at what you've already done. That would also help to illustrate the issue you are having with attributes.

Since your objective is to use this with PHP you also probably should have marked this as an Off Topic thread. I do not personally know the differences in syntax that might exist between PHP & Perl with regard to regex. Are there any? That would certainly effect any conversations we might have on this topic.

use strict;
use warnings;

my ($text, $tag, %tag, %c);

$text = join '', <DATA>;
while ($text =~ /<input (.*?)>/g) {
    $tag = $1;
    while ($tag =~ /(\w+)="(.*?)"/g) {
        $tag{lc($1)} = $2;
    }
    $c{"$tag{type}$tag{name}"} = 1;
}
for (sort keys %c) {
    print "$_\n";
}
print scalar keys %c;

__DATA__
<input type="radio" name="booger" value="bingo">
<input type="radio" name="booger" value="bongo">
<input type="radio" name="snot" value="bingo">
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