wordpress - WooCommerce custom place order validation -

i som additional checks when user has submitted order in woocommerce. have tried using different add_filter methods, seems can't hook place_order filter. have tried with:

add_filter('woocommerce_place_order', 'checkfields'); //on ordersubmit function checkfields(){   if($this != true){     //not allowed place order because of data not true   }else{    //continue order   } } 

but non of above being triggered when submit checkout form. suggestions? :)

try this..

add_action('woocommerce_after_checkout_validation', 'rei_after_checkout_validation');  function rei_after_checkout_validation( $posted ) {      // logics here...     // adding wc_add_notice second parameter of "error" stop form...     // wc_add_notice( __( "omg! you're not human!", 'woocommerce' ), 'error' );      if (empty($_post['captcha'])) {          wc_add_notice( __( "captcha empty!", 'woocommerce' ), 'error' );     }  } 

$posted array this..

array (     [terms] => 0     [createaccount] => 0     [payment_method] => cheque     [shipping_method] =>      [ship_to_different_address] =>      [billing_first_name] =>      [billing_last_name] =>      [billing_company] =>      [billing_email] => iamhuman@gmail.com     [billing_phone] =>      [billing_country] => ph     [billing_address_1] =>      [billing_address_2] =>      [billing_city] =>      [billing_state] =>      [billing_postcode] =>      [order_comments] =>  )