I am trying to replace something at the end of a file, but the replacement is inserted twice. And I don’t understand why.

Demonstration of problem:

$str = "anbncn";
echo preg_replace('/$/', 'inserted', $str);

Returns:

a
b
cinserted     <-- !!
inserted

Is it not possible to match the EOF of a string using regexp identifier $?

I’m not looking for answers how to append strings like .=. My real use case is the following:

$find = '#(R*??>)?$#';
$insert = addcslashes($insert, '\$').'$1';
$content = preg_replace($find, $insert, $content);