PHP: rfc:num_available_processors

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====== PHP RFC: num_available_processors ======
  * Version: 0.1
  * Date: 2025-05-18
  * Author: Daniel Kesselberg, mail@danielkesselberg.de
  * Status: Draft
  * First Published at: https://wiki.php.net/rfc/num_available_processors

===== Introduction =====

The number of available processors is valuable for tools like php-cs-fixer, enabling parallel execution, or when used with semaphores to manage the concurrent execution of resource-intensive tasks. The new num_available_processors function simplifies getting the number of logical processors across various operating systems.

===== Proposal =====


This RFC proposes the addition of a new function that retrieves the number of available processors:

<php>function num_available_processors(): ?int</php>

  * The initial version of this proposal used nproc as the function name, inspired by the idea of adding a similar functionality to PHP. However, the current implementation is simpler than nproc, and to avoid potential differences in behavior, I prefer not to use nproc.
  * The current name in the related PR is num_cpus, inspired by the rust crate num_cpus (https://docs.rs/num_cpus/latest/num_cpus/). However, it could be argued that num_cpus should return the number of physical CPUs, whereas the current implementation returns the number of available processing units.
  * A popular package for php, to obtain the number of processors, uses the name cpu-core-counter.
  * Therefore, I suggest using num_available_processors as the function name. However, I don't have a strong preference on this matter.

===== Backward Incompatible Changes =====

None.

===== Proposed PHP Version(s) =====

Next PHP 8.x


===== RFC Impact =====

This RFC introduces a new function, which might affect existing userland extensions if developers have already created helper functions with the same name. Since the proposed function has a clear and meaningful name, any custom functions should ideally do the same thing and be easy to replace.

There is no impact on SAPIs or the opcache.


===== Future Scope =====

There has already been some discussion on the GitHub pull request. While not currently proposed, a valuable addition could be the introduction of a class such as ReflectionServer or, OS (similar to Node.js, https://nodejs.org/api/os.html) to provide information about the underlying system. Existing functions like sys_getloadavg or php_uname could be integrated into this class.

===== Proposed Voting Choices =====
Include these so readers know where you are heading and can discuss the proposed voting options.

===== Patches and Tests =====

https://github.com/php/php-src/pull/11137 (the current prototype, probably just a rename of the function is necessary)


===== Implementation =====
After the project is implemented, this section should contain 
  - the version(s) it was merged into
  - a link to the git commit(s)
  - a link to the PHP manual entry for the feature
  - a link to the language specification section (if any)

===== References =====
Links to external references, discussions or RFCs

===== Rejected Features =====
Keep this updated with features that were discussed on the mail lists.
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