PHP实现无限级分类（不使用递归）

<?php
 $list = array(
 array(id=>1, fid=>0, title => 中国), 
 array(id=>2, fid=>1, title => 江苏),
 array(id=>3, fid=>1, title => 安徽),
 array(id=>4, fid=>8, title => 江阴),
 array(id=>5, fid=>3, title => 芜湖),
 array(id=>6, fid=>3, title => 合肥),
 array(id=>7, fid=>3, title => 蚌埠),
 array(id=>8, fid=>8, title => 无锡)
 );
?>

<ul>
 <li class="first-child">
 <div>江苏</div>
 <ul>
 <li class="first-child last-child">
 <div>无锡</div>
 <ul>
 <li class="first-child last-child">
 <div>江阴</div>
 </li>
 </ul>
 </li>
 </ul>
 </li>
 <li class="last-child">
 <div>安徽</div>
 <ul>
 <li class="first-child"><div>芜湖</div></li>
 <li><div>合肥</div></li>
 <li class="last-child"><div>蚌埠</div></li>
 </ul>
 </li>
</ul>

<ul><?php echo get_tree_ul($list, 1); ?></ul>

<select>
 <option value="2">江苏</option>
 <option value="8">    无锡</option>
 <option value="4">        江阴</option>
 <option value="3">安徽</option>
 <option value="5">    芜湖</option>
 <option value="6">    合肥</option>
 <option value="7">    蚌埠</option>
</select>

<select>
<?php
 // get_tree_option()返回数组，并为每个元素增加了“深度”（即depth）列，直接输出即可
 $options = get_tree_option($list, 1); 
 foreach($options as $op) {
 echo <option value=" . $op[id] ."> . str_repeat(" ", $op[depth] * 4) . $op[title] . <;/option>;
 }
?>
<;/select>

<?php
 $children = get_tree_child($list, 0);
 echo implode(,, $children); // 输出：1,3,2,7,6,5,8,4
?>

<?php
 $children = get_tree_parent($list, 4);
 echo implode(,, $children); //8, 2, 10
?>

<?php
function get_tree_child($data, $fid) {
 $result = array();
 $fids = array($fid);
 do {
 $cids = array();
 $flag = false;
 foreach($fids as $fid) {
 for($i = count($data) - 1; $i >=0 ; $i--) {
 $node = $data[$i];
 if($node[fid] == $fid) {
 array_splice($data, $i , 1);
 $result[] = $node[id];
 $cids[] = $node[id];
 $flag = true;
 }
 }
 }
 $fids = $cids;
 } while($flag === true);
 return $result;
}

function get_tree_parent($data, $id) {
 $result = array();
 $obj = array();
 foreach($data as $node) {
 $obj[$node[id]] = $node;
 } 

 $value = isset($obj[$id]) ? $obj[$id] : null; 
 while($value) {
 $id = null;
 foreach($data as $node) {
 if($node[id] == $value[fid]) {
 $id = $node[id];
 $result[] = $node[id];
 break;
 }
 }
 if($id === null) {
 $result[] = $value[fid];
 }
 $value = isset($obj[$id]) ? $obj[$id] : null;
 }
 unset($obj);
 return $result;
}

function get_tree_ul($data, $fid) {
 $stack = array($fid);
 $child = array();
 $added_left = array();
 $added_right= array();
 $html_left = array();
 $html_right = array();
 $obj = array();
 $loop = 0;
 foreach($data as $node) {
 $pid = $node[fid];
 if(!isset($child[$pid])) {
 $child[$pid] = array();
 }
 array_push($child[$pid], $node[id]);
 $obj[$node[id]] = $node;
 }

 while (count($stack) > 0) { 
 $id = $stack[0];
 $flag = false;
 $node = isset($obj[$id]) ? $obj[$id] : null;
 if (isset($child[$id])) {
 $cids = $child[$id];
 $length = count($cids);
 for($i = $length - 1; $i >= 0; $i--) {
 array_unshift($stack, $cids[$i]);
 }
 $obj[$cids[$length - 1]][isLastChild] = true;
 $obj[$cids[0]][isFirstChild] = true;
 $flag = true;
 }
 if ($id != $fid && $node && !isset($added_left[$id])) {
 if(isset($node[isFirstChild]) && isset($node[isLastChild])) {
 $html_left[] = <li class="first-child last-child">;
 } else if(isset($node[isFirstChild])) {
 $html_left[] = <li class="first-child">;
 } else if(isset($node[isLastChild])) {
 $html_left[] = <li class="last-child">;
 } else {
 $html_left[] = <li>;
 } 
 $html_left[] = ($flag === true) ? "<div>{$node[title]}</div><ul>" : "<div>{$node[title]}</div>";
 $added_left[$id] = true;
 } 
 if ($id != $fid && $node && !isset($added_right[$id])) {
 $html_right[] = ($flag === true) ? </ul></li> : </li>;
 $added_right[$id] = true;
 }

 if ($flag == false) {
 if($node) {
 $cids = $child[$node[fid]];
 for ($i = count($cids) - 1; $i >= 0; $i--) {
 if ($cids[$i] == $id) {
 array_splice($child[$node[fid]], $i, 1);
 break;
 }
 } 
 if(count($child[$node[fid]]) == 0) {
 $child[$node[fid]] = null;
 }
 }
 array_push($html_left, array_pop($html_right));
 array_shift($stack);
 }
 $loop++;
 if($loop > 5000) return $html_left;
 }
 unset($child);
 unset($obj);
 return implode(, $html_left);
}

function get_tree_option($data, $fid) {
 $stack = array($fid);
 $child = array();
 $added = array();
 $options = array();
 $obj = array();
 $loop = 0;
 $depth = -1;
 foreach($data as $node) {
 $pid = $node[fid];
 if(!isset($child[$pid])) {
 $child[$pid] = array();
 }
 array_push($child[$pid], $node[id]);
 $obj[$node[id]] = $node;
 }

 while (count($stack) > 0) { 
 $id = $stack[0];
 $flag = false;
 $node = isset($obj[$id]) ? $obj[$id] : null;
 if (isset($child[$id])) {
 for($i = count($child[$id]) - 1; $i >= 0; $i--) {
 array_unshift($stack, $child[$id][$i]);
 }
 $flag = true;
 }
 if ($id != $fid && $node && !isset($added[$id])) {
 $node[depth] = $depth;
 $options[] = $node;
 $added[$id] = true;
 }
 if($flag == true){
 $depth++;
 } else {
 if($node) {
 for ($i = count($child[$node[fid]]) - 1; $i >= 0; $i--) {
 if ($child[$node[fid]][$i] == $id) {
 array_splice($child[$node[fid]], $i, 1);
 break;
 }
 } 
 if(count($child[$node[fid]]) == 0) {
 $child[$node[fid]] = null;
 $depth--;
 }
 }
 array_shift($stack);
 }
 $loop++;
 if($loop > 5000) return $options;
 }
 unset($child);
 unset($obj);
 return $options;
}
?>