Change the ‘add to cart’ text in WooCommerce

add_filter( 'woocommerce_product_add_to_cart_text', 'custom_add_to_cart_text' ); // category (archives)
add_filter( 'woocommerce_product_single_add_to_cart_text', 'custom_add_to_cart_text' ); // single
function custom_add_to_cart_text() { 
   return 'My add to cart text';
}

Automatically complete orders in WooCommerce

/**
* Auto Complete all WooCommerce orders.
* Add to theme functions.php file
*/
 
add_action( 'woocommerce_thankyou', 'custom_woocommerce_auto_complete_order' );
function custom_woocommerce_auto_complete_order( $order_id ) {
    global $woocommerce;
 
    if ( !$order_id )
        return;
    $order = new WC_Order( $order_id );
    $order->update_status( 'completed' );
}

Re-order the product tabs in WooCommerce

add_filter( 'woocommerce_product_tabs', 'reorder_woocommerce_product_tabs', 98 );
function reorder_woocommerce_product_tabs( $tabs ) {
   $tabs['reviews']['priority']                = 5;  // Reviews first
   $tabs['description']['priority']            = 10; // Description second
   $tabs['additional_information']['priority'] = 15; // Additional information third
   return $tabs;
}

Hide excerpts for all WordPress posts

add_filter( 'the_excerpt', 'custom_excerpt' );
function custom_excerpt() {
    return '';
}

Control excerpt length in WordPress

function custom_excerpt_length( $length ) {
	return 20;
}
add_filter( 'excerpt_length', 'custom_excerpt_length', 999 );