你有这样的表格

<form action="http://some/url/form_two.php" method="POST">
 <input type="whatever" value="nothing" />
 <input type="hidden" name="form_one_displayed" value="1" />
 <input type="submit" value="Send" />
</form>

在里面form_two.php 验证已发送（或未发送）的数据

<?php
$result = do_some_validation_with( $_POST );

if ( false == $result )
  wp_redirect( \'form_one.php\' );
else
  display_form_two();

function do_some_validation_with( $postdata = array() ) {
  // nothing was send
  if ( empty( $postdata ) )
    return false;

  // if the first form wasn\'t send, stop validation
  if ( ! isset( $postdata[\'form_one_displayed\'] ) )
    return false;

  // do more validation

  // if validation pass
  return true;
}

function display_form_two() {}