- var_dump: documentation ( source)
<?php
$settings = [];
var_dump((array) (!empty($settings['css file']) ? $settings['css file'] : array()));
$settings['css file'] = NULL;
var_dump((array) (!empty($settings['css file']) ? $settings['css file'] : array()));
$settings['css file'] = [];
var_dump((array) (!empty($settings['css file']) ? $settings['css file'] : array()));
$settings['css file'] = ['value'];
var_dump((array) (!empty($settings['css file']) ? $settings['css file'] : array()));
$settings['css file'] = 'string';
var_dump((array) (!empty($settings['css file']) ? $settings['css file'] : array()));