PHP 8.5 introduces pipes, with the following syntax:

<?php
$myString = "Hello World";
$result = $myString
    |> htmlentities(...)
    |> str_split(...)
    |> (fn($x) => array_map(strtoupper(...), $x))
    |> (fn($x) => array_filter($x, fn($v) => $v != 'O'))
    |> (fn($x) => join( ', ', $x));

echo $result, "\n";

Since https://github.com/php/php-src/commit/4d6dde595cda1a34683a050208ffd362fa6e2c43, PHP introduces EXT_STMT opcodes in between each state, with a reference to the TMP variable that holds the value that is sent to the next pipe stage.

Xdebug should expose this value as part of the stack frame.