Regex for special pattern replacement

I need help with a regex.

For a placeholder replacement with PHP I have the following search patterns:

__H1-(.*)__
__H1-(.*)-(.*)__
__H1-(.*)-(.*)-(.*)__
Etc.

I have the following text:

$text ="This is an example __H1-1__ with placeholders __H1-1-2__ that are replaced";

And this is my replace function

$text = preg_replace("/" . $placeholder . "/U", $replace_string, $text);

The problem here is that only the first search pattern is found, but the patterns should be treated differently.

Currently it is so that when finding H1-(.*) both strings in $text (in the second the partial pattern) is replaced.

And another problem is that in the search text could be somethink like this

__H1-1-2-hi____H1-1-2__

in this case ther is only the first pattern found but this are two different patterns:

__H1-1-2-hi__
__H1-1-2__

How can I work around something like this?

The problem with your regex is that .* will also capture - and _ when possible. This is not what you want... so don't allow those:

$placeholder1 = "__H1-([^-_]*)__";
$placeholder2 = "__H1-([^-_]*)-([^-_]*)__";
$placeholder3 = "__H1-([^-_]*)-([^-_]*)-([^-_]*)__";