[PHP-DEV] Proposal for functions that handle prefixes and suffixes

Mailing Lists php.internals
1

Hi

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 :slight_smile:

Cheers

Carlos

2

On 2026-01-16 21:16, Barel wrote:

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

3

Hi

On 1/16/26 20:16, Barel wrote:

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: policies/coding-standards-and-naming.rst at main · php/policies · GitHub

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

4

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.

substr_replace(
array|string $string,
array|string $replace,
array|int $offset,
array|int|null $length = null
): string|array

Contextual usages:

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

Mick

On Sun, 18 Jan 2026, 21:30 Tim Düsterhus, <tim@bastelstu.be> wrote:

Hi

On 1/16/26 20:16, Barel wrote:

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