php recursive example

Recursion as an algorithm is widely used in programming languages. A process or function has a method of directly or indirectly calling itself in its definition or description. It usually transforms a large and complex problem into a smaller problem similar to the original problem to solve. The recursive strategy only A small number of programs are needed to describe the multiple repeated calculations required in the problem-solving process, which greatly reduces the amount of program code.

Here are 4 examples of recursion:

<?php
&#160;&#160; &#160;
&#160;&#160; &#160;/*
&#160;&#160; &#160;&#160;&#160; &#160;递归的实例
&#160;&#160; &#160;&#160;&#160; &#160;1、统计数组元素个数
&#160;&#160; &#160;&#160;   php也可以直接使用count($arr,1) 来计算多维数组的元素的个数
&#160;&#160; &#160;&#160;&#160; &#160;2、统计文件和文件夹数量
&#160;&#160; &#160;&#160;&#160; &#160;3、删除文件或文件夹
&#160;&#160; &#160;&#160;&#160; &#160;用到的系统函数：file_exists()检查目录或者文件是否存在 unlink()删除文件 rmdir()删除目录
&#160;&#160; &#160;&#160;&#160; &#160;4、无限极分类的排序
&#160;&#160; &#160;*/

&#160;&#160; &#160;/**
&#160;&#160; &#160;* 递归共计数组元素个数
&#160;&#160; &#160;* @param array $arr 统计的数组
&#160;&#160; &#160;* @return boolean|int&#160; 如果失败返回false，成功返回数组的元素个数
&#160;&#160; &#160;*/
&#160;&#160; &#160;function conarr($arr){
&#160;&#160; &#160;&#160;&#160; &#160;function funtmp($arr,$sum=0){
&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;if(is_array($arr)){
&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;$sum=count($arr);
&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;}else{
&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;return count($arr);
&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;}
&#160;&#160; &#160;&#160;&#160; &#160;&#160;&#160; &#160;foreach($arr as $k=> $v){
                if(is_array($v)){
                    $sum += funtmp($v,$sum);
                }
            }
            return $sum;
        }
        return funtmp($arr);
    }
    // $arr = array(1,2,3,4,array(1,2,3,array(0,3)));
    // echo conarr($arr).'<br/>';
    // echo count($arr,1);

    /**
    * 递归统计指定目录的子文件的个数和文件夹个数
    * @param $dirname string 目录路径
    * @return array|boolean 返回包含子文件个数和文件夹个数的数组,失败返回false
    */
    function condir($dirname,$data = array('dirnum'=>0,'filenum'=>0)){
        if(!is_dir($dirname)){
            return false;
        }
        $dir = opendir($dirname); //打开句柄
        readdir($dir);//读取点
        readdir($dir);//读取点
        while($filename = readdir($dir)){
            $newfile = $dirname.'/'.$filename;//拼接子文件名
            if(is_dir($newfile)){
                $data['dirnum']++;
                $data['dirnum']+=condir($newfile)['dirnum'];
                $data['filenum']+=condir($newfile)['filenum'];
            }else{
                $data['filenum']++;
            }
        }
        return $data;
    }
    //$a =  condir('C:\wamp\www\test');
    //var_dump($a);

    /**
    * 删除文件或者文件夹
    * @param string $dirname 文件路径
    * @return boolean 删除成功返回true，失败返回false
    */
    function delDir($dirname){
        if(!file_exists($dirname)){return false;}
        if($dir = opendir($dirname)){
            while($filename = readdir($dir)){
                if($filename !="."&& $filename !='..'){
                    $subFile = $dirname.'/'.$filename;
                    if(is_dir($subFile)){
                        delDir($subFile);
                    }
                    if(is_file($subFile)){
                        unlink($subFile);
                    }
                }
            }    
            closedir($dir);
            rmdir($dirname);
        }
        if(!file_exists($dirname)){
            return true;
        }else{
            return false;
        }
    }
    //echo delDir('C:\wamp\www\test');


    //无限极分类排序，父类后跟子类
    function getlist($cate,$pid=0,$html="------",$i=0){
        $i++;
        $list = array();
        foreach($cate as $val){
            if($val['pid']==$pid){
                $val['html']=str_repeat($html,$i-1);
                $list[]=$val;
                $list = array_merge($list,getlist($cate,$val['id'],$html,$i));
            }
        }
        return $list;
    }
?>

The above has introduced PHP recursion examples, including aspects of content. I hope it will be helpful to friends who are interested in PHP tutorials.