is_front_page() && is_home() WordPress Default, Static and Blog Page

if ( is_front_page() && is_home() ) {
 // Default homepage

} elseif ( is_front_page()){
 //Static homepage

} elseif ( is_home()){

//Blog page

} else {

//everything else

}

Get all category ids in WordPress [Array]

Choose either one of these options to Get all category ids in WordPress as an Array

Get all category ids, Option 1

$output_categories = array();
$categories=get_categories($args);
 foreach($categories as $category) { 
 $output_categories[] = $category->cat_ID;
}

Get all category ids, Option 2

$categories_ids = get_terms(
 array( 'category' ), // Taxonomies
 array( 'fields' => 'ids' ) // Fields
);