spatie / laravel-collection-macros

src/macros/validate.php

<?php

use Illuminate\Support\Collection;

/*
 * Returns true if $callback returns true for every item. If $callback
 * is a string or an array, regard it as a validation rule.
 *
 * @param string|callable $callback
 *
 * @return bool
 */
Collection::macro('validate', function ($callback): bool {
    if (is_string($callback) || is_array($callback)) {
        $validationRule = $callback;

        $callback = function ($item) use ($validationRule) {
            if (! is_array($item)) {
                $item = ['default' => $item];
            }

            if (! is_array($validationRule)) {
                $validationRule = ['default' => $validationRule];

Consider using a different name than the imported variable $validationRule, or did you forget to import by reference?

            }

            return app('validator')->make($item, $validationRule)->passes();
        };
    }

    foreach ($this->items as $item) {

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

        if (! $callback($item)) {
            return false;
        }
    }

    return true;
});