wordpress plugin function firing twice - php

Question

Followed through on this post for manipulating woocommerce menu.
This plugin code:
function product_subcategories( $args = array() ) {
$parentid = get_queried_object_id();
$args = array(
'parent' => $parentid
);
$terms = get_terms( 'product_cat', $args );
if ( $terms ) {
echo '<ul class="product-cats">';
foreach ( $terms as $term ) {
echo '<li class="category">';
woocommerce_subcategory_thumbnail( $term );
echo '<h2>';
echo '<a href="' . esc_url( get_term_link( $term ) ) . '" class="' . $term->slug . '">';
echo $term->name;
echo '</a>';
echo '</h2>';
echo '</li>';
}
echo '</ul>';
}
}
add_action( 'woocommerce_before_shop_loop', 'product_subcategories', 50 );
Fires twice.
Why is that??
Thanx
EDIT
Original post link: Display WooCommerce Categories, Subcategories, and Products in Separate Lists

Answer 1

Woocommerce does allow you to register two events with the same tag source. Thus, if the file is loaded twice (e.g. if you use include/require instead of include_once/require_once) it can cause this problem: check it anyhow(!).
The hook itself is called twice in woocommerce, so technically it is possible that the hook is called twice. I do however not know if both templates are loaded in the same call... You might however have registered the call twice w/o knowing: thus check your code for another call to this function, perhaps with a different tag (other than woocommerce_before_shop_loop).

Answer 2

Update:
With your code you are just doing what WooCommerce is already doing, that's why you are seeing duplicated category/subcategory menu items and you say that it's "fired twice".
Anyway, if you keep your code, and then you want to remove that WooCommerce generated category/subcategory items, you can use this hooked function:
add_filter('woocommerce_product_subcategories_args', function( $args ){
$args['taxonomy']= '';
return $args;
});
Code goes in function.php file of your active child theme (or theme) or also in any plugin file.
This will remove the WooCommerce duplicated items…
Original answer:
The woocommerce_before_shop_loop hook:
has no arguments (no need to add $args = array() )
is called many times, but only fired once. Check it replacing your code by this:
add_action( 'woocommerce_before_shop_loop', function(){
wc_print_notice('test message', 'notice');
}, 50 );
Kindly, as your question is not very explicit and detailed, we don't really know what is your problem and can't help you further than that…

Answer 3

While the previous answers are no doubt accurate, I don't think they are truly the reason for multiple calls. I believe the true reason is that you're simply receiving multiple HTTP requests when, to your eyes, it seems like there should only be one. Remember, your plugin is going to load upon every interaction with WP, not just the ones for your application. So /wp-cron.php links, for example, will trigger your plugin "invisibly", as will many other requests like Ajax or JSON calls. Please see https://wordpress.stackexchange.com/questions/170768/wordpress-plugin-executing-code-twice#answer-170784.