PHP regular expression not working with string from database

Question

preg_replace does not return desired result when I use it on string fetched from database.

$result = DB::connection("connection")->select("my query");
foreach($result as $row){

    //prints run-d.m.c.
    print($row->artist . "\n");

    //should print run.d.m.c
    //prints run-d.m.c
    print(preg_replace("/-/", ".", $row->artist) . "\n");
}

This occurs only when i try to replace - (dash). I can replace any other character. However if I try this regex on simple string it works as expected:

$str = "run-d.m.c";

//prints run.d.m.c
print(preg_replace("/-/", ".", $str) . "\n");

What am I missing here?

If you use '/\p{Pd}/' pattern, do you match the hyphen/dash? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 17, 2016 at 8:13
Then, there might be just no - in the string. Not sure if it might help, try also adding /u modifier, /\p{Pd}/u. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 17, 2016 at 8:17
It's likely that what looks like a dash is in reality a minus sign or another kind of dash (which may be different characters). — apokryfos
– apokryfos, Commented Oct 17, 2016 at 8:19

Wiktor Stribiżew · Accepted Answer · 2020-07-13 09:29:00Z

1

It turns out you have Unicode dashes in your strings. To match all Unicode dashes, use

/[\p{Pd}\xAD]/u

See the regex demo

The \p{Pd} matches any hyphen in the Unicode Character Category 'Punctuation, Dash' but a soft hyphen, \xAD, hence it should be combined with \p{Pd} in a character class.

The /u modifier makes the pattern Unicode aware and makes the regex engine treat the input string as Unicode code point sequence, not a byte sequence.

edited Jul 13, 2020 at 9:29

answered Oct 17, 2016 at 8:24

Wiktor Stribiżew

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