spatie / laravel-collection-macros

src/macros/transpose.php

<?php

use Illuminate\Support\Collection;

/*
 * Transpose an array.
 *
 * @return \Illuminate\Support\Collection
 *
 * @throws \LengthException
 */
Collection::macro('transpose', function (): Collection {
    if ($this->isEmpty()) {

The variable $this does not exist. Did you forget to declare it?

        return new static();
    }

    $firstItem = $this->first();

    $expectedLength = is_array($firstItem) || $firstItem instanceof Countable ? count($firstItem) : 0;

    array_walk($this->items, function ($row) use ($expectedLength) {
        if ((is_array($row) || $row instanceof Countable) && count($row) !== $expectedLength) {
            throw new \LengthException("Element's length must be equal.");
        }
    });

    $items = array_map(function (...$items) {
        return new static($items);
    }, ...array_map(function ($items) {
        return $this->getArrayableItems($items);

The variable $this does not exist. Did you forget to declare it?

    }, array_values($this->items)));

    return new static($items);
});