Create a simple shortcode to output the Woocommerce cart count

cart-count-shortcode.php

<?php

// Add cart count shortcode [cart_count]
// =============================================================================

add_shortcode( 'cart_count', 'mb_cart_count' );
function mb_cart_count() {
    if ( class_exists( 'WooCommerce' ) && function_exists( 'WC' ) ) { // Check for WooCommerce and WC() function.
        if ( ! WC()->cart->is_empty() ) {
            return (string) WC()->cart->get_cart_contents_count(); // Cast to string for consistency.
        }
        return '0';
    }
    return '';
}

Might be good to have something like if ( class_exists( 'woocommerce' ) ) { } around this shortcode's code to have it gracefully fail if/when WooCommerce is ever deactivated on the site rather than having it result in a 500 server error due to trying to call a function that's then not available to use (the official documentation at https://woo.com/document/query-whether-woocommerce-is-activated/ shows something similar while creating that full function seemed overkill as we can just check for that class directly here.)

@KZeni Good call, you found an old one here :)