Add support for pipelines with |> and ?|>

[thekid]

This pull request implements support for https://wiki.php.net/rfc/pipe-operator-v3. Additionally, it supports a null-safe version of this operator, ?|>.

Example

$user= $name |> trim(...) |> strtolower(...);

// Equivalent of:
$user= strtolower(trim($name));

Process (initial release)

• Syntactic support, see Add syntactical support for pipelines with |> and ?|> ast#52
• Null-safe version, see Not-Null pipe operator #180
• Emulate pipelines for PHP < 8.5, add to emitter
• Add tests from RFC: Pipe operator php/php-src#17118
• Test with PHP compiled from https://github.com/Crell/php-src/tree/func-composition
• Wait for voting end (May 26th, 2025), see https://externals.io/message/127336 - very likely to pass though!
• Release xp-framework/ast, bump requirement to ^11.6, then release this library
• Update https://github.com/xp-framework/compiler/wiki/Implementation-status

Process (native support)

• Wait for PR to be merged and PHP builds on GitHub to pick this up
• Add PHP 8.5 emitter
• Create feature release

Incompatibility with by-ref arguments

This implementation doesn't raise errors when piping to a callable requiring references like the original (see Zend/tests/pipe_operator/call_by_ref.phpt) for runtime performance reasons. Rejecting references may be seen as a shortcoming of the PHP implementation, see https://externals.io/message/127336#127344

[thekid]

Verified test suite with a PHP built from the current pull request and a PHP85 emitter which does not include the EmulatePipelines trait but instead emits native syntax:

[thekid]

RFC has passed, see https://externals.io/message/127336#127490

[thekid]

Released (albeit without native support, which will have to wait for the php-src PR to be merged) in https://github.com/xp-framework/compiler/releases/tag/v9.5.0

[thekid]

albeit without native support

See PR #187