Replace characters in a PHP string skipping specific domain extensions

Question

I have a long string and would like to replace every dot "." with a question mark, however my string includes domain extensions such as .com which I would like to skip when replacing.

Is there any way I can provide an array such as (".com", ".net", ".org") of phrases to skip when replacing using str_replace() or a similar function?

Input sentence:

$string = "An example of a website would be google.com or similar. However this is not what we are looking for";

The following:

str_replace(".", "?", $string);

Produces:

An example of a website would be google?com or similar? However this is not what we are looking for

Desired output:

An example of a website would be google.com or similar? However this is not what we are looking for

I would like to provide an array of domain extensions to skip, when replacing. Such as:

$skip = array(".com",".net",".org");

and wherever those appear, don't substitute the dot with a question mark.

EDIT: Looks like I need to use a negative lookahead with preg_replace. However not sure how to put it all together: "look for a full stop that is NOT followed by COM or NET or ORG.

You've tagged this with regex and preg replace. Have you tried using regex? I don't see it in your question. — M. Eriksson
– M. Eriksson, Commented Apr 8, 2021 at 13:19
I am not sure what regex to use for it, and can't find anything. — onlybarca6
– onlybarca6, Commented Apr 8, 2021 at 13:20
See stackoverflow.com/questions/2631010/…, namely stackoverflow.com/a/2631107/3832970 — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Apr 8, 2021 at 13:21
Have you done any real research into regex, how it works and tried anything? regex101.com is a very good site for testing (and learning) regex. — M. Eriksson
– M. Eriksson, Commented Apr 8, 2021 at 13:21
@WiktorStribiżew Yes, I've already seen that link, however I'm not sure how to apply it to my needs. Looks like I need to use a negative lookahead, such as (?!.*bar) however not sure how to combine it with: Look for a full stop > that isn't followed by COM or ORG or NET. Can anyone help please? — onlybarca6
– onlybarca6, Commented Apr 8, 2021 at 13:25

Wiktor Stribiżew · Accepted Answer · 2021-04-08 13:35:54Z

1

You need

$result = preg_replace('~\.(?!(?:com|org|net)\b)~', '?', $string);

See the regex demo. Details

\. - a dot
(?! - not followed with
- (?:com|org|net) - com, org, net substrings...
- \b - as whole words (it is a word boundary)
) - end of the negative lookahead.

NOTE: to make the TLDs match in a case insensitive way, add i after the trailing regex delimiter, here, ~i.

See a PHP demo:

$string = "An example of a website would be google.com or similar. However this is not what we are looking for";
$tlds = ['com', 'org', 'net'];
echo preg_replace('~\.(?!(?:' . implode('|', $tlds) . ')\b)~i', '?', $string);
// => An example of a website would be google.com or similar? However this is not what we are looking for

answered Apr 8, 2021 at 13:35

Wiktor Stribiżew

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