Detailed introduction to PHP's unlimited classification and support for outputting tree diagram_PHP Tutorial

/**
* Universal tree class that can generate any tree structure
*/
class tree
{
    /**
* 2-dimensional array required to generate tree structure
* @var array
*/
    var $arr = array();

    /**
* Modification symbols required to generate a tree structure, which can be replaced by images
* @var array
*/
    var $icon = array('│','├','└');

    /**
    * @access private
   */
    var $ret = '';

    /**
* Constructor, initialization class
* @param array 2-dimensional array, for example:
* array(
* 1 => array('id'=>'1','parentid '=>0,'name'=>'First-level column one'),
* 2 => array('id'=>'2','parentid'=>0,'name '=>'First-level column two'),
* 3 => array('id'=>'3','parentid'=>1,'name'=>'Second-level column 1'),
* 4 => array('id'=>'4','parentid'=>1,'name'=>'Second-level column two'),
* 5 => array('id'=>'5','parentid'=>2,'name'=>'Second-level column three'),
* 6 => array('id '=>'6','parentid'=>3,'name'=>'Third-level column one'),
* 7 => array('id'=>'7', 'parentid'=>3,'name'=>'Third-level column two')
* )
*/
    function tree($arr=array())
    {
       $this->arr = $arr;
       $this->ret = '';
       return is_array($arr);
    }

    /**
* Get the parent array
* @param int
* @return array
*/
    function get_parent($myid)
    {
        $newarr = array();
        if(!isset($this->arr[$myid])) return false;
        $pid = $this->arr[$myid]['parentid'];
        $pid = $this->arr[$pid]['parentid'];
        if(is_array($this->arr))
        {
            foreach($this->arr as $id => $a)
            {
                if($a['parentid'] == $pid) $newarr[$id] = $a;
            }
        }
        return $newarr;
    }

    /**
* Get the child array
* @param int
* @return array
*/
    function get_child($myid)
    {
        $a = $newarr = array();
        if(is_array($this->arr))
        {
            foreach($this->arr as $id => $a)
            {
                if($a['parentid'] == $myid) $newarr[$id] = $a;
            }
        }
        return $newarr ? $newarr : false;
    }

    /**
* Get the current position array
* @param int
* @return array
*/
    function get_pos($myid,&$newarr)
    {
        $a = array();
        if(!isset($this->arr[$myid])) return false;
        $newarr[] = $this->arr[$myid];
        $pid = $this->arr[$myid]['parentid'];
        if(isset($this->arr[$pid]))
        {
            $this->get_pos($pid,$newarr);
        }
        if(is_array($newarr))
        {
            krsort($newarr);
            foreach($newarr as $v)
            {
                $a[$v['id']] = $v;
            }
        }
        return $a;
    }

 
    /**
* ----------------------------------------
* Get tree structure
* ----------------------------------------
* @author Midnight(Yang Yunzhou) , yangyunzhou@foxmail.com
* @param $myid means to get all the children under this ID
* @param $str generates the basic code of the tree structure, for example: ""
* @param $sid The selected ID, such as when making a tree drop-down box.
* @param $adds
* @param $ str_group
* @return unknown_type
*/
    function get_tree($myid, $str, $sid = 0, $adds = '', $str_group = '')
    {
        $number=1;
        $child = $this->get_child($myid);
        if(is_array($child))
        {
            $total = count($child);
            foreach($child as $id=>$a)
            {
                $j=$k='';
                if($number==$total)
                {
                    $j .= $this->icon[2];
                }
                else
                {
                    $j .= $this->icon[1];
                    $k = $adds ? $this->icon[0] : '';
                }
                $spacer = $adds ? $adds.$j : '';
                $selected = $id==$sid ? 'selected' : '';
                @extract($a);
                $parentid == 0 && $str_group ? eval("\$nstr = \"$str_group\";") : eval("\$nstr = \"$str\";");
                $this->ret .= $nstr;
                $this->get_tree($id, $str, $sid, $adds.$k.' ',$str_group);
                $number++;
            }
        }
        return $this->ret;
    }
    /**
    * 同上一方法类似,但允许多选
    */
    function get_tree_multi($myid, $str, $sid = 0, $adds = '')
    {
        $number=1;
        $child = $this->get_child($myid);
        if(is_array($child))
        {
            $total = count($child);
            foreach($child as $id=>$a)
            {
                $j=$k='';
                if($number==$total)
                {
                    $j .= $this->icon[2];
                }
                else
                {
                    $j .= $this->icon[1];
                    $k = $adds ? $this->icon[0] : '';
                }
                $spacer = $adds ? $adds.$j : '';

                $selected = $this->have($sid,$id) ? 'selected' : '';
                //echo $sid.'=>'.$id.' : '.$selected.' .
';
                @extract($a);
                eval("\$nstr = \"$str\";");
                $this->ret .= $nstr;
                $this->get_tree_multi($id, $str, $sid, $adds.$k.' ');
                $number++;
            }
        }
        return $this->ret;
    }

    function have($list,$item){
        return(strpos(',,'.$list.',',','.$item.','));
    }
}
?>