I could really go for an array_index() function right now.

01_before.php

<?php

$widgets = array_combine(
    array_map(
        function($widget) {
            return $widget->getId();
        }, 
        $widgets
    ),
    $widgets
);

02_after.php

<?php

$widgets = array_index(function($widget) {
    return $widget->getId();
}, $widgets);

After-after :)

widgets = Hash[widgets.map { |w| [w.id, w] }]

Shameless plug!
You should try my ArrayTools package: https://github.com/axelarge/php-array-tools
Available via composer: https://packagist.org/packages/axelarge/array-tools

$widgets = Arr::indexBy($widgets, function ($widget) { return $widget->getId(); });