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Date: Mon, 23 Feb 2026 20:27:41 +0900
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Subject: [PHP-DEV][DISCUSSION] Limit of code point for grapheme cluster in
 programming languages
To: php internals <internals@lists.php.net>
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From: youkidearitai@gmail.com (youkidearitai)

Hi, Internals

I noticed grapheme cluster is not limit code points in UAX#29.
https://www.unicode.org/reports/tr29/

And there is no limit code point in Unicode that confirmed in issue of ICU.
https://unicode-org.atlassian.net/browse/ICU-23302

So that means create many code points in 1 grapheme cluster,
That is crash for program because computer resource is limited.

For example, this code is 200MB but 1 grapheme cluster in emoji_bomb.txt
```
php -r 'echo(mb_trim(str_repeat("\u{200d}\u{1f468}\u{200d}\u{1f466}\u
{200d}\u{1f466}", 10000000), "\u{200d}"));' -d memory_limit=3D600M >
emoji_bomb.txt
```
(PLEASE BE CAREFUL OPEN IN emoji_bomb.txt BECAUSE MAYBE CRASH)

So, I think we(php-src, programming language level) need to create new
custom limit function.
My idea is below:

```
grapheme_limit_codepoints(string $str, integer $max_codepoints =3D 32): boo=
l
```

I don't have heavy opinion that $max_codepoints is 32.
However, 32 code points is enough of grapheme cluster because
human language max code points is maybe Hak=E1=B9=A3hmalawaraya=E1=B9=81(=
=E0=BD=A7=E0=BE=90=E0=BE=B5=E0=BE=A8=E0=BE=B3=E0=BE=BA=E0=BE=BC=E0=BE=BB=E0=
=BE=82) in
9 code points.

If need more than code points in grapheme cluster,
Userland can to increase $max_codepoints.

Please see also my speakerdeck.
https://speakerdeck.com/youkidearitai/limit-of-code-point-for-grapheme-clus=
ter

What do you think about this idea?

Regards
Yuya

--=20
---------------------------
Yuya Hamada (tekimen)
- https://tekitoh-memdhoi.info
- https://github.com/youkidearitai
-----------------------------