Woocommerce fee not multiplying on multiple cart items?

This script is adding a fee if the product is in a particular category.
The script is working but only for one cart item.
But if there are 2 or more items it wil not multiply in the cart.
What am I doing wrong?

add_action( 'woocommerce_cart_calculate_fees','custom_pcat_fee', 20, 1 );
function custom_pcat_fee( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    // iPhone CAT
    $iphone_categories = array('74');
    $iphone_fee_amount = 0;
    
    // iPad CAT
    $ipad_categories = array('75');
    $ipad_fee_amount = 0;

    
    // Loop through cart items 
    foreach( $cart->get_cart() as $cart_item ){
        $quantiy = $cart_item['quantity']; //get quantity from cart
        if( has_term( $iphone_categories, 'product_cat', $cart_item['product_id']) )
            $iphone_fee_amount = 4.70 * $quantiy;
        if( has_term( $ipad_categories, 'product_cat', $cart_item['product_id']) )
            $ipad_fee_amount = 2.60 * $quantiy;
    }

    // Adding the fee for iPhone
    if ( $iphone_fee_amount > 0 ){
        // Last argument is related to enable tax (true or false)
        WC()->cart->add_fee( __( "Thuiskopieheffing iPhone", "woocommerce" ), $iphone_fee_amount, true );
    }
    // Adding the fee for iPad
    if ( $ipad_fee_amount > 0 ){
        // Last argument is related to enable tax (true or false)
        WC()->cart->add_fee( __( "Thuiskopieheffing iPad", "woocommerce" ), $ipad_fee_amount, true );
    }
}```

Answer

I think you missing basic summation in foreach. you override $iphone_fee_amount and $ipad_fee_amount you have to append each value to that variable. check the code below.

function custom_pcat_fee( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    // iPhone CAT
    $iphone_categories = array('74');
    $iphone_fee_amount = 0;
    
    // iPad CAT
    $ipad_categories = array('75');
    $ipad_fee_amount = 0;

    
    // Loop through cart items 
    foreach( $cart->get_cart() as $cart_item ){
        $quantiy = $cart_item['quantity']; //get quantity from cart
        if( has_term( $iphone_categories, 'product_cat', $cart_item['product_id']) )
            $iphone_fee_amount = $iphone_fee_amount + ( 4.70 * $quantiy );
        if( has_term( $ipad_categories, 'product_cat', $cart_item['product_id']) )
            $ipad_fee_amount = $iphone_fee_amount + ( 2.60 * $quantiy );
    }

    // Adding the fee for iPhone
    if ( $iphone_fee_amount > 0 ){
        // Last argument is related to enable tax (true or false)
        WC()->cart->add_fee( __( "Thuiskopieheffing iPhone", "woocommerce" ), $iphone_fee_amount, true );
    }
    // Adding the fee for iPad
    if ( $ipad_fee_amount > 0 ){
        // Last argument is related to enable tax (true or false)
        WC()->cart->add_fee( __( "Thuiskopieheffing iPad", "woocommerce" ), $ipad_fee_amount, true );
    }
}