(sf-dump)

Symfony Var Dumper Documentation:

    https://symfony.com/doc/current/components/var_dumper.html

But you don't need Symfony framework to use var dumper. You can just install it with composer.

https://packagist.org/packages/symfony/var-dumper

/* CSS rules */

.sf-dump { display: none !important; }
.sf-dump-show { display: block !important; }

// JavaScript statements

$('.sf-dump').addClass('sf-dump-show'); // to show debug info

$('.sf-dump').removeClass('sf-dump-show'); // to hide debug info