pipe.php

<?php

class p {
  private array $callables = [];
  public function __construct(private $value) {}
  public function p(callable $callable) { $this->callables[] = $callable;return $this;}
  public function __invoke() { foreach($this->callables as $callable) $this->value=$callable($this->value);return $this->value;}
}

$remove = ['noindex'];
print (new p('noindex, follow'))
->p(fn ($x) => explode(', ', $x))
->p(fn ($x) => array_diff($x, $remove))
->p(fn ($x) => implode(', ', $x))
();