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Date: Tue, 1 Aug 2017 08:29:31 +0200
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To: Andreas Hennings <andreas@dqxtech.net>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] New functions: string_starts_with(), string_ends_with()
From: michal@brzuchalski.com (=?UTF-8?Q?Micha=C5=82_Brzuchalski?=)

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Hi Andreas,

2017-08-01 6:57 GMT+02:00 Andreas Hennings <andreas@dqxtech.net>:

> Hello list,
> a quite common use case is that one needs to find out if a string
> $haystack begins or ends with another string $needle.
> Or in other words, if $needle is a prefix or a suffix of $haystack.
>
> One prominent example would be in PSR-4 or PSR-0 class loaders.
> Maybe the use case also occurs when writing parsers..
> In each of these two examples (parsers, class loaders), we care about
> performance.
>
> (forgive me if this was discussed before, I did not find it anywhere
> in the archives)
>
> --------------------------
>
> Existing solutions to this problem feel non-trivial, and/or are
> suboptimal in performance.
> https://stackoverflow.com/questions/2790899/how-to-
> check-if-a-string-starts-with-a-specified-string
> https://stackoverflow.com/questions/834303/startswith-
> and-endswith-functions-in-php
> This answer compares different solutions,
> https://stackoverflow.com/a/7168986/246724
>
> Existing solutions:
> (Let's focus on string_starts_with(), the other case is mostly
> equivalent / symmetric)
>
> if (0 =3D=3D=3D strpos($haystack, $needle)) {..}
> I have often seen this presented as the preferable solution.
> Unfortunately, this searches the entire string, not just the
> beginning. Especially if $haystack is really long, this can be a
> waste.
> E.g. if (0 =3D=3D=3D strpos(file_get_contents('some_source_file.php'),
> '<?php')) {..} will search the entire file for an occurence of
> '<?php'.
>
> if ($needle =3D=3D=3D substr($haystack, 0, strlen($needle))) {..}
> This reserves new memory for the substring, which later needs to be
> garbage-collected.
> Also, this requires an additional function call to strlen() - which
> adds even more clutter if $needle is an expression, not just a
> variable.
>
> if (0 =3D=3D=3D strncmp($haystack, $needle, strlen($needle))) {..}
> Needs the additional call to strlen().
> Otherwise, this seems like a really good solution.
>
> if ('' =3D=3D=3D $needle || false !=3D=3D strrpos($haystack, $needle,
> -strlen($haystack))) {..}
> This is the funky solution from https://stackoverflow.com/a/
> 10473026/246724
> The author says that it will be outperformed by strncmp() - so..
>
> if (preg_match('/^' . preg_quote($needle, '/') . '/', $haystack)) {..}
> Clearly gonna be slower than other options.
>
> As said, all these solutions do work, but they are either suboptimal,
> or they add clutter and overhead, or feel a bit like mind acrobatics.
>
> -----------------
>
> So, I wonder if it would be worthwhile to add new functions
> string_starts_with() / string_has_prefix(), and string_ends_with() /
> string_has_suffix().
>
> (Or maybe change strncmp(), so that the 3rd parameter $len is
> optional. If $len is NULL / not provided, it would use the length of
> the second (or first?) string.
> (idea was that second parameter =3D needle).)
>
> For me personally, I am sure that I would use a new
> string_starts_with() a lot more often than a lot of the other existing
> string functions.
> I don't think it is an exotic or niche use case.
>
> --------------
>
> Spinning this further:
> A lot of times if I want to check if $haystack begins with $needle, I
> will then need the rest of the string after $needle.
> So
> if (string_starts_with($haystack, $needle)) {
>     $suffix =3D substr($haystack, strlen($needle));
> }
> or
> if (string_ends_with($filename, '.php')) {
>     $basename =3D substr($filename, 0, -4);
> }
>
> I wonder if this could be somehow combined.
> E.g.
> if (FALSE !=3D=3D $basename =3D string_clip_suffix($filename, '.php')) {
>     // Do something with $basename.
> }
>
> ------------------
>
> One flaw of these new functions would be that they are less versatile
> than other string functions.
> They solve this problem, and nothing else.
> On the other hand, this is the point, to avoid unnecessary overhead.
>
> The other problem would be, of course, "feature creep" aka "we have so
> many string functions already".
> This is a matter of opinion.
> I would imagine the "cost" of new native functions is:
> - global namespace pollution
> - increased mental load to learn and remember all of them
> - higher memory footprint of php engine?
> - more C code to maintain
> - a new doc page.
> Did I miss something?
>
> ------------------
>
> -- Andreas
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>
This idea was discussed 11 months ago https://externals.io/message/94787
There is also a proper RFC
https://wiki.php.net/rfc/add_str_begin_and_end_functions
You might wanna contact with Will to get feedback from the idea.

--=20
regards / pozdrawiam,
--
Micha=C5=82 Brzuchalski
about.me/brzuchal
brzuchalski.com

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