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Date: Mon, 18 Jan 2021 11:32:20 +0100
Message-ID: <CAF+90c_D5c_5pyHx6Wxus2w6qcxnQfoFMreaRWukDkx+K=Wntg@mail.gmail.com>
To: Adam Cable <adam@adsar.co.uk>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Addition of substring and subistring functions.
From: nikita.ppv@gmail.com (Nikita Popov)

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On Wed, Jan 13, 2021 at 11:51 AM Adam Cable <adam@adsar.co.uk> wrote:

> Hi internals.
>
> I've been coding in PHP for 15 years now, and spend most days using it to
> transform content into meaningful data.
>
> Most of this is pulling out prices and attributes of certain products from
> HTML, for example, grabbing the price from content such as "Total price
> including delivery: &pound;15.00".
>
> To grab the "15.00" from the string can take quite a few lines of PHP and
> can be pretty cumbersome.
>
> I've built some helper functions - substring, and it's case-insensitive
> variant subistring to help.
> Functions take in the string plus a to and from string, and return a trim'd
> string found between the two.
>
> So substring("Total price including delivery: &pound;15.00", "&pound;", "")
> would return "15.00".
> From and to strings are optional and therefore return from the beginning or
> to the end.
>
> In the past I hadn't thought about adding this to PHP core, but with the
> introduction of str_starts/ends_with functions in PHP 8.0 I thought it may
> be useful to include the sub(i)string building blocks too.
>
> Implementation and tests can be found @
> https://github.com/php/php-src/pull/6602
>
> I'm sure the C implementation can be made a lot better, but it seems to
> work
> OK at present.
>
> This is my first e-mail to internals, so please excuse my naivety with
> things, but hope this is useful.
>
> Thanks,
> Adam
>

Hi Adam,

A few thoughts:
1. The name of the function is not clear. It's not obvious what the
difference between substr() and substring() is. To make it worse,
JavaScript has both substr() and substring(), but the meaning of
substring() there is a different one from what you propose. I think a
better name would be something like str_between().
2. Why does this perform an implicit trim() call? I understand that this
may be useful in some cases, but it will also limit applicability of the
function. It's easy to write trim(substring(...)), but if the trim() is
part of the call, there's no way to avoid it.
3. More generally, I feel that this API is a bit too specific for inclusion
in the standard library. It can certainly be useful, but I don't think it's
anywhere near as ubiquitous as operations like str_ends_with(). For complex
string matching tasks, I would probably pick preg_match() over a
combination of str* functions anyway.

Regards,
Nikita

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