这是一个老问题，但现在有了。。但形式结束（仅限）。

WP版本4.3.0-文件“/WP admin/user new.php”-第330行

/**
 * Fires at the end of the new user form.
 *
 * Passes a contextual string to make both types of new user forms
 * uniquely targetable. Contexts are \'add-existing-user\' (Multisite),
 * and \'add-new-user\' (single site and network admin).
 *
 * @since 3.7.0
 *
 * @param string $type A contextual string specifying which type of new user form the hook follows.
 */
do_action( \'user_new_form\', \'add-existing-user\' );

add_action(\'user_new_form\', \'addmycustomfield\');
function addmycustomfield() {
?>
<table class="form-table">
<tr>
<th scope="row">My test field:</th>
<td><input type="text" size="32" name="testfield" value="<?php echo get_option(\'madeup_wp_option\'); ?>" /></td>
</tr>
</table> 
<?php
}

我可以通过一个相当脆弱的黑客来做到这一点。它使用输出缓冲区插入新字段。谢天谢地，这里有一个很好的钩子来拯救球场。

// FRAGILE!  This rewrites code directly in the buffer, upgrading WP may break this
function wpse18772_add_fields( $buffer ) {
  $input_html = \'<input type="text" name="your-new-field" id="your-new-field">\';

  // will insert a new field after "role"
  $buffer = preg_replace( \'~<label\\s+for="role">(.*?)</tr>~ims\', \'<label for="role">$1</tr><tr class="form-field"><th>My New Field</th><td>\' . $input_html . \'</td></tr>\', $buffer );

  return $buffer;
}

function wpse18772_buffer_start() { ob_start("wpse18772_add_fields");  }
function wpse18772_buffer_end() { ob_end_flush(); }
add_action(\'admin_head\', \'wpse18772_buffer_start\', 10, 1);
add_action(\'admin_footer\', \'wpse18772_buffer_end\', 10, 1);

function wpse18772_save_fields($user_id) {
  if($_POST[\'action\'] != "adduser" && $_POST[\'action\'] != "createuser") return;

  if(!empty($_POST[\'your-new-field\'])) {
    // save field to meta, or do whatever you want to here
  }
}
add_action(\'user_register\', \'wpse18772_save_fields\');

See this answer. 没有挂钩，但可以使用jQuery来实现。只需使用jQuery添加html标记，就可以了。