How determine path above website in PHP?

<?php //this for highlighting
//Let's try to figure out where we are and where we want things to go
define('BASE_PATH',realpath('.').'/');  //figure out where we are
echo 'Base path : '.BASE_PATH.'<br/>';  //same as MODX_BASE_PATH
$temproot = dirname($_SERVER["DOCUMENT_ROOT"]).'/';  //figure out document root path
echo 'Temp root : '.$temproot.'<br/>'; 

if (strpos(BASE_PATH,'public_html/')>0) 
{
  $prefix = 'public_html/';
  $numchars =  strpos(BASE_PATH,$prefix);
  $newroot = substr(BASE_PATH, 0, $numchars);  //trim that off
  $tempwhereweare = substr(BASE_PATH, $numchars+strlen($prefix), strlen(BASE_PATH));
}
else
{
  $newroot = $temproot;  //assume we are on Windows/XAMPP
  $tempwhereweare = substr(BASE_PATH, strlen($temproot));
}
define('BASE_ROOT', $newroot);
echo 'BASE_ROOT : '.BASE_ROOT.'<br/>';

echo 'Temp where we are : '.$tempwhereweare.'<br/>';
if (strpos($tempwhereweare,'htdocs\\') !== FALSE)
{
  $prefix = 'htdocs/';
  $newwhereweare = str_replace($prefix, '', $tempwhereweare);
}  
else
  $newwhereweare = $tempwhereweare;

define('WHEREWEARE', $newwhereweare);

echo 'Base root : '.BASE_ROOT.'<br/>';
echo 'Where we are : '.WHEREWEARE.'<br/>';

//define file structures for backup location
$structure1 = BASE_ROOT.$backupfolder.WHEREWEARE.'manager/includes/';
$structure2 = BASE_ROOT.$backupfolder.WHEREWEARE.'assets/';
echo 'Structure 1 : '.$structure1.'<br/>';
echo 'Structure 2 : '.$structure2.'<br/>';

//At this point we should have enough info to create backup directories
//  above the root and we should know where we are putting files

//try creating file structures for backup location
if (!mkdir($structure1, 0755, true)) {
    echo 'Failed to create folders in first list.  They may already exist?<br/>';
}
if (!mkdir($structure2, 0755, true)) {
    echo 'Failed to create folders in second list.    They may already exist?<br/><br/>';
}
//make sure file structures exist
if (file_exists($structure1) && file_exists($structure2))
{
	//where files are going to be coming from
	$backup_locn = BASE_ROOT.$backupfolder.WHEREWEARE;
	//where files are going to be going
	$target_locn = BASE_ROOT.$prefix.WHEREWEARE;

$backupIndex = $modx->getOption('backup_index_path')

$backupfolder = ".blah/";
$whereweare = dirname(__FILE__);

echo $whereweare."<br/>";

if (strpos($whereweare, 'public_html/') !== FALSE)
{
	$prefix = 'public_html/';

}
elseif (strpos($whereweare, 'htdocs\\') !== FALSE)
{
	$prefix = 'htdocs\\';
}
else
{
	echo "Unknown<br/>";
}

$pos = strpos($whereweare, $prefix);
$upper_locn = substr_replace($whereweare, $backupfolder, $pos, strlen($whereweare));
echo $upper_locn;