* 支付回调支付币种 | 传入参 | 说明 | | --- | --- | | type | \[ 必填 \] 币种代码 | | 回调参 | 说明 | | --- | --- | | [string] | 回调币种 | * 案例 ~~~ $WX_applet->back_currency($fee_type); ~~~