How to show child page without providing ID so it's dynamic

Question

So this is my code. This piece of code shows me the child page titles. But i'm providing the ID from the parent page. Is there a way to make this dynamic? I don't want to use the ID cuz then its static..

  <?php
                  $childArgs = array(
                      'sort_order' => 'ASC',
                      'sort_column' => 'menu_order',
                      'child_of' => 127
                  );
                  $childList = get_pages($childArgs);
                  foreach ($childList as $child) { ?>

        <ul class="menu-items menu-level-1 menu-count-5">
          <li class="menu-item item-number-1  item-number-2 item-number-3 item-number-4 item-number-5 item-id-84283 item-odd item-page item-node item-alias-over-ons-de-winkel"><a href=""><?php echo $child->post_title; ?></a></li>
        <?php } ?>

Answer 1

//The correct code

functions.php

  function get_page_parent_id( $id ) {
$args = array(
  'sort_order' => 'ASC',
  'sort_column' => 'menu_order',
  'child_of' => $id
);
$args = get_pages($args);

if(is_array($pages))
  $pageID = $id;
else {
  $pageID = wp_get_post_parent_id( $id );
}

return $pageID;


}
 ?>

page.php

<?php
          $parentID = get_page_parent_id(get_the_ID());

            $childArgs = array(
            'sort_order' => 'ASC',
            'sort_column' => 'menu_order',
            'child_of' => $parentID
          ); ?>
    <div class="subnav">
      <h3 class="subnav-headline"><a href="/over-ons" class="c-dark"><?php echo get_the_title($parentID); ?></a></h3>

        <ul class="menu-items menu-level-1 menu-count-5">
             <?php $pages = get_pages($childArgs);
                foreach($pages as $page ) { ?>
          <li class="menu-item item-number-2 item-id-84286 item-even item-page item-node item-alias-over-ons-geschiedenis-leonidas"><a href="<?php echo get_the_permalink($page);?>"><?php echo $page->post_title;?></a></li>
            <?php   }   ?>
      </ul>
    </div>

Answer 2

Try the following:

<?php

  global $post;

  $page_id = get_the_id();

  $childArgs = array(
    'sort_order' => 'ASC',
    'sort_column' => 'menu_order',
    'child_of' => $page_id
  );
  $childList = get_pages($childArgs);

  if($childList && (!$post->post_parent || is_page(127))){ ?>
    <ul class="menu-items menu-level-1 menu-count-5">
      <?php foreach ($childList as $child) { ?>
        <li class="menu-item item-number-1  item-number-2 item-number-3 item-number-4 item-number-5 item-id-84283 item-odd item-page item-node item-alias-over-ons-de-winkel">
          <a href=""><?php echo $child->post_title; ?></a>
        </li>
      <?php } ?>
    </ul>
  <?php } ?>