page.update:before

/site/config/config.php

return [
    'hooks' => [
        'page.update:before' => function (Kirby\Cms\Page $page, array $values, array $strings) {
            // your code goes here
        }
    ]
]

Parameters

Parameter	Type
$page	Kirby\Cms\Page
$values	array
$strings	array

Note that the page.update:before hook is only called when the content of the page content is updated, not when the slug, title, status etc. are changed.