Looking for the author of GetChildID

<?php
$docid = (isset($docid)) ? $docid: $modx->documentIdentifier;

$children= $modx->getActiveChildren($docid, 'id', 'ASC');
foreach($children as $value){
 if($value['pagetitle']==$childsName){
    $childsID= $value['id'];
    return $childsID;    
    break;
 }
}
?>

<?php
$docid = (isset($docid)) ? $docid: $modx->documentIdentifier;

while ($children= $modx->getChildIds($docid, 1)) {
    $childID= reset($children);
    $docid= $childID;
}
return $docid;
?>

<?php
// docid param sets the document to start from (uses current document if not set)
$docid = (isset($docid)) ? $docid: $modx->documentIdentifier;
// depth param optionally sets the depth limit to get the child id from (default 100)
$depth = (isset($depth) && intval($depth)) ? intval($depth) : 0;

// set limit to an arbitrary maximum depth
$limit= 100;
if ($depth) {
    // if depth is set, set the limit to depth
    $limit= $depth;
}
// while above the depth limit and there are more children,
//   get the docid of the child and decrement the limit
while ($limit > 0 && $children= $modx->getChildIds($docid, 1)) {
    $childID= reset($children);
    $docid= $childID;
    $limit--;
}
return $docid;
?>