mysql> SELECT * FROM tree;
+----+----------+
| id | parentID |
+----+----------+
|  1 |     NULL |
|  2 |        1 |
|  3 |        1 |
|  4 |        1 |
|  5 |        2 |
|  6 |        3 |
|  7 |        2 |
|  8 |        5 |
|  9 |        4 |
+----+----------+

<?php
header("content-type: text/plain");
 
/**
 * A recursive function that prints a tree-structure.
 * @global <mysqli> $dbLink A open MySQLI connection. 
 * @param <number> $level Used to determine how far from the root the current ID is.
 * @param <number> $parentID The ID the current recursion uses as a root.
 */
function printTree($level=0, $parentID=null)
{
    global $dbLink;
 
    // Create the query
    $sql = "SELECT id FROM tree WHERE ";
    if($parentID == null) {
        $sql .= "parentID IS NULL";
    }
    else {
        $sql .= "`parentID`=" . intval($parentID);
    }
 
    // Execute the query and go through the results.
    $result = $dbLink->query($sql);
    if($result)
    {
        while($row = $result->fetch_assoc())
        {
            // Print the current ID;
            $currentID = $row['id'];
            for($i = 0; $i < $level; $i++) {
                echo " ";
            }
            echo $currentID . PHP_EOL;
 
            // Print all children of the current ID
            printTree($level+1, $currentID);
        }
        $result->close();
    }
    else {
        die("Failed to execute query! ($level / $parentID)");
    }
}
 
// Open a MySQLI connection and execute the function.
$dbLink = new mysqli("host", "usr", "passwd", "dbName");
printTree();
$dbLink->close();
?>

1
 2
  5
   8
  7
 3
  6
 4
  9

Structure:
                                      ID(1)
                                         /\
                               ID(2)       ID(3)
                                 /\              /\
                          ID(4) ID(5) ID(6) ID(7)
 
Example:
                                         A
                                         /\
                                      B    C
                                     /\     /\
                                   D  E  F  G

                      headcode
                     /      \
                  code1     code2
                /      \
       newcode1      newcode2
      /       \
thirdcode1   thirdcode2

    function GetDownline($member_id,$direction) 
    { 
$getdownlinesql = @mysql_fetch_assoc(@mysql_query('select memberid,placementid,position from `yourrelationaltable` where placementid="'.$member_id.'" and  position="'.$direction.'"'));
$getdownline = $getdownlinesql['memberid'];
return $getdownline; 
    }
 
then simply call it with:
$firstleft = GetDownline('headmemberidhere','Left'); //for first left
$firstright = GetDownline('headmemberidhere','Right'); //for first right
echo $firstleft;
echo $firstright;

$secondleftofleft = GetDownline($firstleft,'Left'); //for second left of first left
$secondrightofleft = GetDownline($firstleft,'Right'); //for second right of first left
 
echo $secondleftofleft;
echo $secondrightofleft;
 
$secondleftofright = GetDownline($firstright,'Left'); for second left of first right
$secondrightofright = GetDownline($firstright,'Right'); for second right of first right
 
echo $secondleftofright;
echo $secondrightofright;

<?php
include("../includes/config.php"); 
//my database connection is set in my config, otherwise, just create your own db connect
$defaultmcode = 'yourdefaultidhere';
if($_GET['topmcode']){
$topmcode = trim($_GET['topmcode']);
}else{
$topmcode = $defaultmcode;
}
$topmcode = ltrim($topmcode);
$topmcode = rtrim($topmcode);
$topmcode = strtoupper($topmcode);
//my memberid are alphanumerics and all caps so I had to conver all to upper case, else, comment the above strtoupper call
 
//get Downline of a Member, this function is needed so that you can simply call left or right of the memberid you are looking for
		function GetDownline($member_id,$direction) 
		{ 
				$getdownlinesql = @mysql_fetch_assoc(@mysql_query('select memid,placementid,position from `yourtablehere` where placementid="'.$member_id.'" and  position="'.$direction.'"'));
				$getdownline = $getdownlinesql['memid'];
				return $getdownline; 
		}
 
//get the child of the member, this section will look for left or right of a member, once found, it will call GetNextDownlines() function to assign new memberid variables for left or right
    function GetChildDownline($member_id) 
    { 
				$getchilddownlinesql = @mysql_query('select memid,placementid,position from `yourtablehere` where placementid="'.$member_id.'" ORDER BY position');
				while($childdownline = mysql_fetch_array($getchilddownlinesql)){
						$childdownlinecode = $childdownline['memid'];
						$direction = $childdownline['position'];
						if($direction=='L'){
							if($childdownlinecode){
								//this is where you play with your html layout
								echo $childdownlinecode.'<br>';
								GetNextDownlines($childdownlinecode,'L');
							}
						}
 
							if($direction=='R'){
								if($childdownlinecode){
									//this is where you play with your html layout
									echo $childdownlinecode.'<br>';
									GetNextDownlines($childdownlinecode,'R');
							}
						}
				 }
    }
 
//recursive function to call the functions and start all over again, this is where you can get the newly assigned memberid, call the GetChildDownline() that gets the left or right, then recycle all codes
    function GetNextDownlines($member_id,$direction) 
    {
			if($direction=='L'){
					$topleft = GetDownline($member_id,'L');
						if($topleft){
								//this is where you play with your html layout
						echo $topleft.'<br>';
						}
							$getleftdownlinesql = @mysql_query('select memid,placementid,position from `yourtablehere` where placementid="'.$topleft.'" ORDER BY position');
							while($getleftdownline = mysql_fetch_array($getleftdownlinesql)){
							$leftdownline = $getleftdownline['memid'];
							$leftdirection = $getleftdownline['position'];
 
							if($leftdirection=='L'){
									if($leftdownline){
								//this is where you play with your html layout
										echo $leftdownline.'<br>';
										GetChildDownline($leftdownline);
									}
							  }
 
							if($leftdirection=='R'){
									if($leftdownline){
								//this is where you play with your html layout
									echo $leftdownline.'<br>';
									 GetChildDownline($leftdownline);
									 }
							   }
							 }
			}
 
 
			if($direction=='R'){
						$topright = GetDownline($member_id,'R');
						if($topright){
						echo $topright.'<br>';
						}
						$getrightdownlinesql = @mysql_query('select memid,placementid,position from `yourtablehere` where placementid="'.$topright.'" ORDER BY position');
						while($getrightdownline = @mysql_fetch_array($getrightdownlinesql)){
									$rightdownline = $getrightdownline['memid'];
									$rightdirection = $getrightdownline['position'];
 
									if($rightdirection=='L'){
											if($rightdownline){
								//this is where you play with your html layout
											echo $rightdownline.'<br>';
											GetChildDownline($rightdownline);
											}
									}
 
									if($rightdirection=='R'){
											if($rightdownline){
								//this is where you play with your html layout
											echo $rightdownline.'<br>';
											GetChildDownline($rightdownline);
											}
									}
 
							}
				}
}
 
?>
<html>
	<head>
	<title>Genealogy</title>
	<meta http-equiv=Content-Type content="text/html; charset=utf-8">
	<meta http-equiv=content-language content=en>
	<link href="styles.css" type=text/css rel=stylesheet>
	</head>
<body>
<table cellpadding="0" cellspacing="0" width="100%" border="0" class="noborder">
 <tr>
	<td>
<?php
echo $topmcode.'<br>';
GetNextDownlines($topmcode,'L');
GetNextDownlines($topmcode,'R');
?>
 
	</td>
 </tr>
</table>
</body>
</html>

<?php
/**
 * Handles creating and/or printing a Tree-Like HTML output, complete with
 * all necessary CSS styles.
 *
 * Assumes a MySQL database table structure like so:
 *  CREATE TABLE `name` (
 *    `id` int(11) NOT NULL AUTO_INCREMENT,
 *    `parentID` int(11) DEFAULT NULL,
 *    PRIMARY KEY (`id`)
 *  );
 *
 * Public methods:
 *   createTree - Returns the HTML tree-view.
 *   printTree  - Prints the HTML tree-view.
 *
 * Private methods
 *   fetchTree  - Reads the complete tree structure into an array.
 *   buildHtml  - Builds the HTML div hierarchy based.
 */
class TreeView
{
    private $bgColor = "rgba(0, 100, 0, 0.10)";
 
    private $dbLink;
    private $tblName;
 
    /**
     * Default constructor
     * @param mysqli $dbLink A open MySQL (mysqli) connection.
     * @throws Exception
     */
    public function __construct(mysqli $dbLink)
    {
        if($dbLink != null && $dbLink->connect_errno == 0)
        {
            $this->dbLink = $dbLink;
 
            // This number is added the the container DIV ID, so that we can
            // tell the DIVs a part if there are more than one view created.
            if(!isset($GLOBALS['TreeView_DivID'])) {
                $GLOBALS['TreeView_DivID'] = 0;
            }
        }
        else
        {
            throw new Exception("The mysqli object provided is invalid.");
        }
    }
 
    /**
     * Creates a descending tree-like view of the tree-structure in the given
     * database table and returns it as a string.
     * @param <type> $tblName The name of the database table to use.
     * @return <string> The string output.
     * @throws Exception
     */
    public function createTree($tblName)
    {
        if(!isset($dbName, $tblName) || (empty($dbName) && empty($tblName)))
        {
            throw new Exception("Failed to create the tree. Table or database information is invalid");
        }
        else
        {
            // Set up variables
            $this->tblName = $tblName;
            $treeData = array();
            $output = "";
 
            // Create the output
            $this->fetchTree($treeData);
 
            // Set up the CSS styles, and create the container DIV.
            $divID = "TreeView_ContainerDiv_" . $GLOBALS['TreeView_DivID'];
            $output = <<<HTML
<style type="text/css">
    div#{$divID}     { margin: 0; padding: 0; text-align: center; }
    div#{$divID} div { margin: 0; padding: 0 10px; float: left; background-color: {$this->bgColor}; }
    div#{$divID} p   { margin: 0; padding: 0; }
</style>
<div id="{$divID}">
HTML;
 
            // Add the DIV hierachy.
            $this->buildHtml($treeData, $output);
 
            // Increment the DIV ID number
            $GLOBALS['TreeView_DivID']++;
 
            return $output;
        }
    }
 
    /**
     * Prints a descending tree-like view of the tree-structure in the given
     * database table.
     * @param <type> $tblName The name of the database table to use.
     * @throws Exception
     */
    public function printTree($tblName)
    {
        echo $this->createTree($tblName);
    }
 
    /**
     * A recursive function that fetches a tree-structure from a database into an array.
     * @global <mysqli> $dbLink A open MySQLI connection.
     * @param <number> $parentID The ID the current recursion uses as a root.
     */
    private function fetchTree(&$parentArray, $parentID=null)
    {
        global $dbLink;
 
        // Create the query
        if($parentID == null) {
            $parentID = -1;
        }
        $sql = "SELECT `id` FROM `{$this->tblName}` WHERE `parentID`= ". intval($parentID);
 
        // Execute the query and go through the results.
        $result = $dbLink->query($sql);
        if($result)
        {
            while($row = $result->fetch_assoc())
            {
                // Create a child array for the current ID
                $currentID = $row['id'];
                $parentArray[$currentID] = array();
 
                // Print all children of the current ID
                $this->fetchTree($parentArray[$currentID], $currentID);
            }
            $result->close();
        }
        else {
            die("Failed to execute query! ($level / $parentID)");
        }
    }
 
    /**
     * Builds a HTML <div> hierarchy from the tree-view data.
     * Each parent is encased in a <div> with all their child nodes, and each
     * of the children are also encased in a <div> with their children.
     * @param <array> $data The tree-view data from the fetchTree method.
     * @param <string> $output The <div> hierachy.
     */
    private function buildHtml($data, &$output)
    {
        // Add the DIV hierarchy.
        foreach($data as $_id => $_children)
        {
            $output .= "<div><p>{$_id}</p>";
            $this->buildHtml($_children, $output);
            $output .= "</div>";
        }
    }
}
?>

<!DOCTYPE html>
<html>
    <head>
        <title>Tree-view Test</title>
        <meta http-equiv="Content-Type" content="text/html; charset=utf8">
    </head>
    <body>
        <?php
        $dbLink = new mysqli("localhost", "usr", "pwd", "dbName");
 
        $treeView = new TreeView($dbLink);
        $treeView->printTree('tblName');
 
        $dbLink->close();
        ?>
    </body>
</html>