PHP Recursive infinite Pole classification

There are several forms of recursive infinite class classification, and here are just a few examples of the three common types:

The first type: Returns an array with a sort:

<?php$data = Array (1 = = Array (' id ' = = 1, ' pid ' = 0, ' user_name ' = ' one ',),        2 = = Array (' id ' = = 2, ' pid ' = 1, ' user_name ' + ', '), 3 = = Array (        ' id ' = 3, ' pid ' = 1, ' user_name ' + ', ', ' 4 = ' array (' id ' = = 4,        ' pid ' = 2, ' user_name ' = ' three ', ' 5 = = Array ' (' id ' = 5, ' pid ' = 2, ' user_name ' = ' three ',), 6 = = Array (' id ' = = 6, ' pid ' = 5, ' user_name ' = ' f ')    we ',),); function gencate ($data, $pid = 0, $level = 0) {Static $result = array (); $result = ($level = = 0)?    Array (): $result; $prefix = ($level = = 0)?    ": Str_repeat ('-', $level); foreach ($data as $key + $row) {if ($row [' pid '] = = $pid) {$row [' user_name '] = $prefix. $row ['            User_name '];          $result [] = $row [' user_name '];  Gencate ($data, $row [' id '], $level + 1); }} return $result;} Echo ' <pre> '; $result = Gencate ($data);p rint_r ($result); exit; >

The second type: Returns the HTML string form:

function gettreehtml ($data, $pId) {    $html = ';    foreach ($data as $k = + $v) {        if ($v [' pid '] = = $pId) {             $html. = "<li>". $v [' user_name '];            $html. = Gettree ($data, $v [' id ']);            $html = $html. "</li>";        }    }    Return $html? ' <ul> '. $html. ' </ul> ': $html;}

The third type: Returns a multidimensional array form:

function Gettreearray ($data, $pId = 0) {    $tree = array ();    foreach ($data as $key + $value) {        if ($value [' pid '] = = $pId) {            $value [' childrens '] = Gettree ($data, $v alue[' id ']);            $tree [] = $value;        }    }    return $tree;}