Proposal for functions that handle prefixes and suffixes

7 months ago by Barel — view source — reply

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I have just created a PR with the implementation of six new functions which
can be used to manage suffixes and prefixes in strings. I did not actually
plan to create the PR just yet, I just wanted to add the implementation as
a sample of what I wanted to achieve and wanted to create the PR in my own
fork but somehow I managed to actually create it in the main repo.

This is the PR https://github.com/php/php-src/pull/20953

Nevertheless, the idea is that in php code many times we have to deal with
prefixes or suffixes of strings, this comes up a lot when you are dealing
with file names or urls. Some examples

If the domain includes a initial www part, remove it
If the filename includes the .png extension, remove it
If the URL does not include the http:// schema, add it
If the URL is missing a trailing slash, add it
If the URL starts with http://, change it to https://
If the filename ends in .jpeg, change it to .jpg
etc...

It is not too difficult to implement this functionality by using the
str_starts_with, str_ends_with and the substr functions or with
preg_replace but I think it would be good to have some functions that can
perform these operations in a single step, creating code which is simpler
to write and to understand

My proposal adds six functions:

function add_prefix(string $source, string $prefix): string
function add_suffix(string $source, string $suffix): string

Add a prefix or suffix to a string only if the string does not yet have it

function remove_prefix(string $source, string $prefix): string
function remove_suffix(string $source, string $suffix): string

Remove a prefix or suffix from a string if the string has it

function replace_prefix(string $source, string $prefix, string $replace):
string
function replace_suffix(string $source, string $suffix, string $replace):
string

Replace a prefix or suffix in a string it the string has it

I would like to know if the internals people think that the addition of
these functions would be interesting. If there is some interest I will
prepare a full RFC

This is my first contribution to php-src so I would be grateful for any
advice or hints :-)

Cheers

Carlos

7 months ago by Juris Evertovskis — view source — reply

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function add_prefix(string $source, string $prefix): string
function add_suffix(string $source, string $suffix): string

Add a prefix or suffix to a string only if the string does not yet
have it

Hi,

As the functions do not always add a prefix, I'd suggest to consider
names like ensure_prefix or enforce_prefix instead.

Something like ensure_str_starts_with or ensure_starts_with would be
a nicer fit with the str_starts_with, but then it doesn't rhyme with
the other prefix/suffix functions that well.

Otherwise I can only say that I've had to solve the same tasks in
multiple projects, so I'd enjoy such functions being available in PHP
itself.

BR,
Juris

7 months ago by tim@bastelstu.be — view source — reply

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Nevertheless, the idea is that in php code many times we have to deal with
prefixes or suffixes of strings, this comes up a lot when you are dealing
with file names or urls. Some examples

From the back of my mind I seem to remember that this was previously
proposed with similar use cases, since I can remember saying the same
I'm saying here before:

Filenames and URLs are probably the worst possible use case for this
feature, since they are “structured” strings where naively performing
string operations at best just results in garbage and at worst result in
security issues.

If the domain includes a initial www part, remove it

This just seems unsafe, since you are likely making assumptions about
URLs you don't own.

If the filename includes the .png extension, remove it

basename($filename, ".png");

If the URL does not include the http:// schema, add it

Simply adding a prefix will break URLs that already have a scheme. Use
PHP 8.5's URI extension instead.

If the URL is missing a trailing slash, add it

If the URL starts with http://, change it to https://

URI extension.

If the filename ends in .jpeg, change it to .jpg

Here you probably want to have more than one mapping (e.g. .htm to
.html), so you would probably use a combination of pathinfo() and a
lookup table.

function replace_prefix(string $source, string $prefix, string $replace):
string
function replace_suffix(string $source, string $suffix, string $replace):
string

Replace a prefix or suffix in a string it the string has it

This parameter order is inconsistent with both str_replace and
preg_replace, which are likely the two closest existing functions we have.

Naming-wise these functions should definitely start with a
str_(pre|suf)fix_ prefix for proper grouping and autocompletion. Thus:

str_prefix_add()
str_prefix_remove()
str_prefix_replace()
str_suffix_add()
str_suffix_remove()
str_suffix_replace()

And of course Juris correctly pointed out that 'add' is misleading,
because the behavior is conditional.

I would like to know if the internals people think that the addition of
these functions would be interesting. If there is some interest I will
prepare a full RFC

For the reasons mentioned above, I don't see much value in the proposal.
Personally I've rarely needed the functionality in the past and the
cases where I needed it, it was a common enough operation that I could
just place it in a function myself.

Best regards
Tim Düsterhus

7 months ago by mickmackusa — view source — reply

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I don't recall ever needing to ensure prefixes or suffixes, but I have
wanted to prepend or append a string to an array of strings. Maybe there is
some demand for "ensuring" when working with phone numbers or product SKUs.
I don't know.

Whatever logic is required for a given scenario, does this need to be built
into the core? I once asked about adding array_transpose() to the core, and
the response boiled down to: PHP doesn't need a core function for every
possible data manipulation.

Topically, circa 2024-03-24, I proposed to modify substr_replace() which is
a solid go-to for prepending, but not appending. (Subject: "Proposal: Make
$offset of substr_replace null by default") This is because the offset
parameter does not accept null. Food for thought.

Contextual usages:

[Add prefix string to each value of a flat array][
https://stackoverflow.com/a/78210830/2943403]

-[Fastest way to add a prefix to all array keys?][
https://stackoverflow.com/a/76196482/2943403]

[Regex to Add a postfix to each item of a PHP array][
https://stackoverflow.com/a/79083258/2943403]

Mick

Hi

Nevertheless, the idea is that in php code many times we have to deal
with
prefixes or suffixes of strings, this comes up a lot when you are dealing
with file names or urls. Some examples

From the back of my mind I seem to remember that this was previously
proposed with similar use cases, since I can remember saying the same
I'm saying here before:

Filenames and URLs are probably the worst possible use case for this
feature, since they are “structured” strings where naively performing
string operations at best just results in garbage and at worst result in
security issues.

If the domain includes a initial www part, remove it

This just seems unsafe, since you are likely making assumptions about
URLs you don't own.

If the filename includes the .png extension, remove it

basename($filename, ".png");

If the URL does not include the http:// schema, add it

Simply adding a prefix will break URLs that already have a scheme. Use
PHP 8.5's URI extension instead.

If the URL is missing a trailing slash, add it

If the URL starts with http://, change it to https://

URI extension.

If the filename ends in .jpeg, change it to .jpg

Here you probably want to have more than one mapping (e.g. .htm to
.html), so you would probably use a combination of pathinfo() and a
lookup table.

function replace_prefix(string $source, string $prefix, string $replace):
string
function replace_suffix(string $source, string $suffix, string $replace):
string

Replace a prefix or suffix in a string it the string has it

This parameter order is inconsistent with both str_replace and
preg_replace, which are likely the two closest existing functions we have.

Naming-wise these functions should definitely start with a
str_(pre|suf)fix_ prefix for proper grouping and autocompletion. Thus:

str_prefix_add()

str_prefix_remove()

str_prefix_replace()

str_suffix_add()

str_suffix_remove()

str_suffix_replace()

See also the corresponding policy:

https://github.com/php/policies/blob/main/coding-standards-and-naming.rst#functions

And of course Juris correctly pointed out that 'add' is misleading,
because the behavior is conditional.

I would like to know if the internals people think that the addition of
these functions would be interesting. If there is some interest I will
prepare a full RFC

For the reasons mentioned above, I don't see much value in the proposal.
Personally I've rarely needed the functionality in the past and the
cases where I needed it, it was a common enough operation that I could
just place it in a function myself.

Best regards
Tim Düsterhus