Woocommerce conditional is_product() from functions.php - php

Question

I want to check if is single product page, but this has no effect on single product page:
if (! is_admin() && is_product() ) {
var_dump('is product'); // this has no effect in single product page
}
Is there a limitation to use is_product() in functions.php? How can I achieve this?
EDIT:
In order to avoid var_dump issues, this is the final code I'm trying. It try to add product type (simple/variable) to body class:
add_action( 'woocommerce_after_single_product', function () {
if (! is_admin() && is_product() ) {
add_filter( 'body_class', function( $classes ) {
global $post;
$product = wc_get_product( $post->ID );
$tipo = $product->get_type();
return array_merge( $classes, array( $tipo ) );
});
}
}, 100 );

Answer 1

You can not use this function directly without a hook since your functions.php file is included before every other file - mostly. To make this thing work you need to work with hooks every time like this:
add_action( 'template_redirect', 'template_redirect_action' );
function template_redirect_action() {
if ( ! is_admin() && is_product() ) {
add_filter( 'body_class', function ( $classes ) {
global $post;
$product = wc_get_product( $post->ID );
$tipo = $product->get_type();
return array_merge( $classes, array( $tipo ) );
} );
}
}
Visit a product page and check your body classes.
By using the template_redirect hook you can be sure it's executed on every page. Otherwise your check would not make any sense when using a product hook which only gets executed on product pages.
Tested an works.