EDIT

ADDING

PHP / MYSQL Web Hosting at:<br>
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<?
	$db = mysql_connect("HOSTNAME", "USERNAME", "PASSWORD");
	mysql_select_db("DATABASE_NAME",$db);
if ($_GET['id']) {
  if(isset($_REQUEST['Submit'])) {
  	$sql = "SELECT * FROM mptt where id=".$_GET['id'];
  	$result = mysql_query($sql ,$db);
  	$row = mysql_fetch_array($result);
  	$right = $row['right'];
  	// UPDATE RIGHT VALUES
  	$sql = "UPDATE mptt SET `right`=`right`+2 WHERE `right` > ". ($right - 1);
  	if(!$result = mysql_query($sql ,$db)) echo "$sql <br>".mysql_error();
  	// UPDATE LEFT VALUES
  	$sql = "UPDATE mptt SET `left`=`left`+2 WHERE `left` > ". ($right - 1);
  	if(!$result = mysql_query($sql ,$db)) echo mysql_error();
  	// INSERT NEW CATEGORY
  	$sql = "INSERT INTO mptt (`left`,`right`,`title`) values ('".$right."', '".($right +1)."', '".$_REQUEST['title']."')";
  	if(!$result = mysql_query($sql ,$db)) echo mysql_error();
  } else {
  	?>
	<form name="form1" method="post" action="<? echo $_SERVER['REQUEST_URI']; ?>">
  	Title: <input type="text" name="title">
	<input type="submit" name="Submit" value="Submit">
	</form>
	<?
  }
  } 
function display_mptt($root) {
  global $db;
  echo '<table border="0" width="200">';
  // retrieve the left and right value of the $root node
  $sql2 = "SELECT * from mptt where id=$root";
  //$sql = "SELECT left,right FROM mptt WHERE `id`=1";
  $result2 = mysql_query($sql2 ,$db);
  if(!$row2 = mysql_fetch_array($result2)) echo mysql_error();
  echo '<h1>Modified Preorder Tree Traversal</h1>';
  // start with an empty $right stack
  $right = array();
 // now, retrieve all descendants of the $root node
  $sql = "SELECT * from mptt WHERE `left` BETWEEN ".$row2['left']." AND ".$row2['right']." ORDER BY 'left' ASC";
  $result = mysql_query($sql ,$db);
 // display each row
  while ($row = mysql_fetch_array($result)) {
  	// only check stack if there is one
  	if (count($right)>0) {
  		// check if we should remove a node from the stack
  		while ($right[count($right)-1]<$row['right']) {
  			array_pop($right);
  		}
  	}
 // display indented node title
  echo '<tr><td>'.str_repeat('&nbsp;&nbsp;',count($right)).$row['title'].'</td><td><a href="'.$_SERVER['PHP_SELF'].'?id='.$row['id'].'">[ add ]</a></td></tr>';
 // add this node to the stack
  $right[] = $row['right'];
  }
  echo '</table>';
} 
  
  display_mptt(1);
  echo "<hr>";
?>
 

INDENTED ORDER DISPLAYING

PHP / MYSQL Web Hosting at:<br>
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<?
	$db = mysql_connect("HOSTNAME", "USERNAME", "PASSWORD");
	mysql_select_db("DATABASE_NAME",$db);

	echo '<hr>'; 
	function display_mptt($root) {
	global $db;
	// retrieve the left and right value of the $root node
	$sql2 = "SELECT * from mptt where id=$root";

	$result2 = mysql_query($sql2 ,$db);
	if(!$row2 = mysql_fetch_array($result2)) echo mysql_error();
	echo '<h1>Indentation</h1>';

	// start with an empty $right stack
	$right = array();

	// now, retrieve all descendants of the $root node
  	$sql = "SELECT * from mptt WHERE `left` BETWEEN ".$row2['left']." AND ".$row2['right']." ORDER BY 'left' ASC";
 	$result = mysql_query($sql ,$db);

 	// display each row
  	while ($row = mysql_fetch_array($result)) {
  		// only check stack if there is one
  		if (count($right)>0) {
  			// check if we should remove a node from the stack
  			while ($right[count($right)-1]<$row['right']) {
  				array_pop($right);
  			}
  		}
 	// display indented node title
  	echo str_repeat('&nbsp;',count($right)).$row['title']."<br>";
 	// add this node to the stack
  	$right[] = $row['right'];
  }
 } 
  
  display_mptt(1);
  ?>

Indentation
food
  fruit
    red
      cherry
    yellow
      banana
  meat
    beef
    pork

DISPLAYING

<?
	$db = mysql_connect("HOSTNAME", "USERNAME", "PASSWORD");
	mysql_select_db("DATABASE_NAME",$db);

	$sql = "SELECT title FROM mptt WHERE `left` BETWEEN 2 AND 11";
  	$result = mysql_query($sql ,$db);

  	if ($myrow = mysql_fetch_array($result)) {
  		do {
  			echo $myrow['title'].'<BR>';
  		} while ($myrow = mysql_fetch_array($result));
  	}else{
  		echo '<strong>ERROR: </strong>'.mysql_error();
  	}
  	
?>

Modified Preorder Tree Transversal Totorial