Disable only flat rate shipping method when free shipping is available in Woocommerce

I am using Hide specifics Flat Rates when Free Shipping is available in WooCommerce 3 lightly changed answer code to hide all shipping methods except one. The only method I want showing is a rate from the “Woocommerce Advanced Shipping” plugin.

I am using the correct rate ID etc…

Everything works fine except when a customer tries to click that shipping method, it won’t stay selected. It just jumps back to free shipping.

I have tried debugging and also tried the code with a native woocommerce flat rate ID and it showed up/able to select it just fine.

add_filter( 'woocommerce_package_rates', 'conditionally_hide_shipping_methods', 100, 2 );
function conditionally_hide_shipping_methods( $rates, $package ) {

    $flat_rates_express = array( '2588' );

    $free = $flat2 = array();
    foreach ( $rates as $rate_key => $rate ) {
        // Updated Here To 
        if ( in_array( $rate->id, $flat_rates_express ) )
            $flat2[ $rate_key ] = $rate;
        if ( 'free_shipping:12' === $rate->id )
            $free[ $rate_key ] = $rate;
    }
        return ! empty( $free ) ? array_merge( $free, $flat2 ) : $rates;
}

ID I want to Keep Shown: “2588” (Custom Shipping Rate From Plugin)

How can I disable the Flat rate shipping method when free shipping is available o and keep a custom shipping rate (from a plugin)?

Answer

As you have 3 shipping methods, 1 free shipping, 1 flat rate and 1 custom ‘2588’, it’s possible to hide the flat rate shipping method when free shipping is available instead:

add_filter( 'woocommerce_package_rates', 'free_shipping_disable_flat_rate', 1000, 2 );
function free_shipping_disable_flat_rate( $rates, $package ) {
    // Here your free shipping rate Id
    $free_shipping_rate_id = 'free_shipping:12';

    // When your Free shipping method is available
    if ( array_key_exists( $free_shipping_rate_id, $rates ) ) {
        // Loop through shipping methods rates
        foreach ( $rates as $rate_key => $rate ) {
            // Removing "Flat rate" shipping method
            if ( 'flat_rate' === $rate->method_id ){
                unset($rates[$rate_key]);
            }
        }
    }
    return $rates;
}

Code goes in functions.php file of your active child theme (or active theme). Tested and works.

Refresh the shipping caches:

1. This code is already saved on your function.php file.
   
2. In a shipping zone settings, disable / save any shipping method, then enable back / save.
   You are done and you can test it.