如果价格超过500，则禁用BACS支付网关

I'm trying to disable the bacs gateway if the customers cart total is over £500.

I have this code here which I've placed into my storefront functions.php file

add_filter('woocommerce_available_payment_gateways','filter_gateways',1);
function filter_gateways($gateways){
global $woocommerce;

$min_cart_total = 500;

$cart_total = ($woocommerce->cart->get_cart_total());
$cart_total = ereg_replace("[^0-9]", "", $cart_total)/100;

if ($cart_total > $min_cart_total){
    unset($gateways['bacs']);
}

return $gateways;
}

But the options for bacs still shows up at the end even if my cart total is £250 for example.

Is there anything I'm doing wrong here?

I'm not sure about your ereg_replace code, but I think you should for sure be using a later priority:

add_filter('woocommerce_available_payment_gateways','filter_gateways', 20);
function filter_gateways($gateways){

$min_cart_total = 500;

$cart_total = WC()->cart->cart_contents_total; // the total without wc_price formatting

if ($cart_total > $min_cart_total){
    unset($gateways['bacs']);
}

return $gateways;
}

Your code was running first, and the Woo code was probably running later and adding the gateway back to the available gateways.

Doesn't impact anything yet, but the global $woocommerce is deprecated in favor of WC().