Question

First off, if it’s not clear from the tag, I’m doing this in PHP – but that probably doesn’t matter much.

I have this code:

$inputStr = strip_tags($inputStr);
$inputStr = preg_replace("/[^a-zA-Z\s]/", " ", $inputStr);

Which seems to remove all HTML tags and virtually all special and non-alphabetic characters perfectly. The one problem is, for some reason, it doesn’t filter out carraige return/line feeds (just the combination).

If I add this line:

$inputStr = preg_replace("/\s+/", " ", $inputStr);

at the end, however, it works great. Can someone tell me:

1. Why doesn’t the first preg_replace filter out the CR/LFs?
2. What this second preg_repalce is actually doing? I understand the first one for the most part, but hte second one is confusing me – it works but I don’t know why.
3. Can I combine them into 1 line somehow?

Answer 1

Your first regex is removing all characters that are not letters or whitespace. CRLFs are whitespace, so they aren’t filtered out.

The second one is replacing whitespace with a space character. Essentially it condenses sequences of whitespace into a single space (due to the quantifier being greedy).

I suggest removing the \s from the first regex, see if that works.