A friend just asked me to write a PHP function to list all the contents of a directory and its sub-directories.
Nothing special here... just a simple example piece of code and boredom...

function ListContents($DirName)
{
	print '<ul>';
	$dir=opendir($DirName);
	while($file=readdir($dir))
		if($file!='.' && $file!='..')
		{
			$FilePath="$DirName/$file";
			$IsDir=is_dir($FilePath);
			print "<li>$file [".($IsDir ? 'D' : number_format(filesize($FilePath), 0, '.', ',')).']';
			if($IsDir)
				ListContents($FilePath);
			print '</li>';
		}
	closedir($dir);
	print '</ul>';
}

It wouldn’t be a bad idea to turn off PHP’s “output buffering” and on “implicit flush” when running something like this for larger directories.
Example output for “ListContents('c:\\temp');”:

I decided to make it a little nicer afterwards by bolding the directories, adding their total size, and changing sizes to a human readable format. This function is a lot more memory intensive because it holds data in strings instead of immediately outputting.

function HumanReadableSize($Size)
{
	$MetricSizes=Array('Bytes', 'KB', 'MB', 'GB', 'TB');
	for($SizeOn=0;$Size>=1024 && $SizeOn<count($MetricSizes)-1;$SizeOn++) //Loops until Size is < a binary thousand (1,024) or we have run out of listed Metric Sizes
		$Size/=1024;
	return preg_replace('/\\.?0+$/', '', number_format($Size, 2, '.', ',')).' '.$MetricSizes[$SizeOn]; //Forces to a maximum of 2 decimal places, adds comma at thousands place, appends metric size
}

function ListContents2($DirName, &$RetSize)
{
	$Output='<ul>';
	$dir=opendir($DirName);
	$TotalSize=0;
	while($file=readdir($dir))
		if($file!='.' && $file!='..')
		{
			$FilePath="$DirName/$file";
			if(is_dir($FilePath)) //Is directory
			{
				$DirContents=ListContents2($FilePath, $DirSize);
				$Output.="<li><b>$file</b> [".HumanReadableSize($DirSize)."]$DirContents</li>";
				$TotalSize+=$DirSize;
			}
			else //Is file
			{
				$FileSize=filesize($FilePath);
				$Output.="<li>$file [".HumanReadableSize($FileSize).']</li>';
				$TotalSize+=$FileSize;
			}
		}
	closedir($dir);
	$RetSize=$TotalSize;
	$Output.='</ul>';
	return $Output;
}

Example output for “print ListContents2('c:\\temp', $Dummy);”:

The memory problem can be rectified through a little extra IO by calculating the size of a directory before its contents is listed, thereby not needing to keep everything in a string.

function CalcDirSize($DirName)
{
	$dir=opendir($DirName);
	$TotalSize=0;
	while($file=readdir($dir))
		if($file!='.' && $file!='..')
			$TotalSize+=(is_dir($FilePath="$DirName/$file") ? CalcDirSize($FilePath) :  filesize($FilePath));
	closedir($dir);
	return $TotalSize;
}

function ListContents3($DirName)
{
	print '<ul>';
	$dir=opendir($DirName);
	$TotalSize=0;
	while($file=readdir($dir))
		if($file!='.' && $file!='..')
		{
			$FilePath="$DirName/$file";
			$IsDir=is_dir($FilePath);
			$FileSize=($IsDir ? CalcDirSize($FilePath) : filesize($FilePath));
			$TotalSize+=$FileSize;
			print '<li>'.($IsDir ? '<b>' : '').$file.($IsDir ? '</b>' : '').' ['.HumanReadableSize($FileSize).']';
			if($IsDir) //Is directory
				$TotalSize+=ListContents3($FilePath);
			print '</li>';
		}
	closedir($dir);
	print '</ul>';
}

Example output: for “ListContents3('c:\\temp');”:

Of course, after all this, my friend took the original advice I gave him before writing any of this code, which was that using bash commands might get him to his original goal much easier.