<?php
/**
 * Array2ArrayTree
 * @package   
 * @author Gaurav Jassal
 * @copyright <a href="http://www.gauravjassal.com">http://www.gauravjassal.com</a>
 * @version 1.0
 * @access public
 */
class Array2ArrayTree
{
    public $arrOriginal = array();
    public $arrDummy = array();
    public $strKey = "";
    /**
     * Array2ArrayTree::__construct()
     * 
     * @param $arrData Array
     * @param $arrKey String 
     * @return
     */
    public function __construct($arrData, $arrKey)
    {
        $this->arrOriginal = $arrData;
        $this->strKey = $arrKey;
        $this->arrDummy = array();
    }

    /**
     * Array2ArrayTree::makeTree()
     * 
     * @return Array
     */
    public function makeTree()
    {
        for ($i = 0; $i <= sizeof($this->arrOriginal) - 1; $i++) {
            $keyPosition = $this->searchKey($this->arrOriginal[$i][$this->strKey]);
            if ($keyPosition == -1) {
                $this->addNode($this->arrOriginal[$i]);
            } else {
                $this->appendNode($this->arrOriginal[$i], $keyPosition);
            }
        }
        return $this->arrDummy;
    }
    /**
     * Array2ArrayTree::searchKey()
     * 
     * @param $strCurrentValue String
     * @return
     */
    function searchKey($strCurrentValue)
    {
        for ($i = 0; $i <= sizeof($this->arrDummy) - 1; $i++) {
            if ($this->arrDummy[$i][0][$this->strKey] == $strCurrentValue) {
                return $i;
            }
        }
        return - 1;
    }
    /**
     * Array2ArrayTree::addNode()
     * 
     * @param $arrNode Array
     * @return
     */
    function addNode($arrNode)
    {
        $this->arrDummy[sizeof($this->arrDummy)][0] = $arrNode;
    }
    /**
     * Array2ArrayTree::appendNode()
     * 
     * @param $arrNode Array
     * @param $keyPosition Integer
     * @return
     */
    function appendNode($arrNode, $keyPosition)
    {
        array_push($this->arrDummy[$keyPosition], $arrNode);
    }
}
?>
Usage

<?php
require_once("array2arraytree.php");
$arrProducts=array(
                array(
                "product_id" 			=> "007",
                "product_name"      	=> "Blackberry R-900 Mobile",
                "product_price" 		=> "£450",
                "product_status"		=>"1",
                "product_category"		=>"Mobile"
                ),
				array(
                "product_id" 			=> "033",
                "product_name"      	=> "8 GB Pendrive",
                "product_price" 		=> "£14.99",
                "product_status"		=> "0",
                "product_category"		=> "Computers"
                ),
				array(
                "product_id" 			=> "033",
                "product_name"      	=> "The White Tiger – Aravind Adiga",
                "product_price" 		=> "£29.99",
                "product_status"		=> "1",
                "product_category"		=> "Books"
                ),
				array(
                "product_id" 			=> "4501",
                "product_name"      	=> "The Final Reckoning - Sam Bourne",
                "product_price" 		=> "£19.99",
                "product_status"		=> "0",
                "product_category"		=> "Books"
                ),
				array(
                "product_id" 			=> "001",
                "product_name"      	=> "Wespro Multi-SIM & Touch-screen Mobile",
                "product_price" 		=> "£150",
                "product_status"		=> "1",
                "product_category"		=> "Mobile"
                ),
				array(
                "product_id" 			=> "004",
                "product_name"      	=> "Sigmatel MP4/MP3 + Camera Mobile",
                "product_price" 		=> "£150",
                "product_status"		=> "1",
                "product_category"		=> "Mobile"
                ),
				array(
                "product_id" 			=> "034",
                "product_name"      	=> "The Final Reckoning - Sam Bourne",
                "product_price" 		=> "£15.79",
                "product_status"		=> "0",
                "product_category"		=> "Books"
                ),
				array(
                "product_id" 			=> "334",
                "product_name"      	=> "250 GB Portable Hard Drive",
                "product_price" 		=> "£79.99",
                "product_status"		=> "1",
                "product_category"		=> "Computers"
                )
			);

$objTree=new Array2ArrayTree($arrProducts,"product_category");
$arrTree=$objTree->makeTree();
print("<pre>");
print_r($arrTree);
print("</pre>");
?>

http://www.gauravjassal.com/index.php/site/entry/filter_array_into_categorized_format/

Filter Array into Categorized format

PHP