php session工作原理分析

<?php
/**
* 通用的树型类，可以生成任何树型结构
*/
class tree
{
 /**
 * 生成树型结构所需要的2维数组
 * @var array
 */
 var $arr = array();

 /**
 * 生成树型结构所需修饰符号，可以换成图片
 * @var array
 */
 var $icon = array('│','├','└');

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

 /**
 * 构造函数，初始化类
 * @param array 2维数组，例如：
 * array(
 *      1 => array('id'=>'1','parentid'=>0,'name'=>'一级栏目一'),
 *      2 => array('id'=>'2','parentid'=>0,'name'=>'一级栏目二'),
 *      3 => array('id'=>'3','parentid'=>1,'name'=>'二级栏目一'),
 *      4 => array('id'=>'4','parentid'=>1,'name'=>'二级栏目二'),
 *      5 => array('id'=>'5','parentid'=>2,'name'=>'二级栏目三'),
 *      6 => array('id'=>'6','parentid'=>3,'name'=>'三级栏目一'),
 *      7 => array('id'=>'7','parentid'=>3,'name'=>'三级栏目二')
 *      )
 */
 function tree($arr=array())
 {
       $this->arr = $arr;
    $this->ret = '';
    return is_array($arr);
 }

    /**
 * 得到父级数组
 * @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;
 }

    /**
 * 得到子级数组
 * @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;
 }

    /**
 * 得到当前位置数组
 * @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;
 }

 /**
  * -------------------------------------
  *  得到树型结构
  * -------------------------------------
  * @author  Midnight(杨云洲),  yangyunzhou@foxmail.com
  * @param $myid 表示获得这个ID下的所有子级
  * @param $str 生成树形结构基本代码, 例如: "<option value=$id $select>$spacer$name</option>"
  * @param $sid 被选中的ID, 比如在做树形下拉框的时候需要用到
  * @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))
  {
      $total = sqlserver/42852.htm target=_blank >count($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.'&nbsp;',$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.' : '.$selected.' . <br/>';
    @extract($a);
    eval("$nstr = "$str";");
    $this->ret .= $nstr;
    $this->get_tree_multi($id, $str, $sid, $adds.$k.'&nbsp;');
    $number++;
   }
  }
  return $this->ret;
 }

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

function selectSort($arr,$style)
             {
                 $temp=0;
                 for($i=0;$i<count($arr)-1;$i++)
                 {
                     for($j=$i+1;$j<count($arr);$j++)
                     {
                         if($style=='bts') $op=$arr[$i]<$arr[$j];
                         else if($style=='stb') $op=$arr[$i]>$arr[$j];
                         if($op)
                         {
                             $temp=$arr[$i];
                             $arr[$i]=$arr[$j];
                             $arr[$j]=$temp;
                         }
                     }
                 }
                 foreach ($arr as $key => $value)
                 {
                     echo $value.',';   
                 }
             }
             $arr1=array(21.5,33,90,7,-4,5,55,11);
             selectSort($arr1,'stb');

function maoPao($arr,$style)    {
                 $temp=0;
                 for($i=0;$i<count($arr)-1;$i++)
                 {
                     for($j=0;$j<count($arr)-1-$i;$j++)
                     {
                         if($style=='bts') $op=$arr[$j]<$arr[$j+1];
                         else if($style=='stb') $op=$arr[$j]>$arr[$j+1];
                         if($op)
                         {
                             $temp=$arr[$j];
                             $arr[$j]=$arr[$j+1];
                             $arr[$j+1]=$temp;
                         }
                     }
                 }
                 foreach ($arr as $key => $value)
                 {
                     echo $value.',';   
                 }
             }
             $arr1=array(101,101,-9,-8,0,76,1,57,43,90,23,-56);
             maoPao($arr1,'stb');//small to big

function insertSort($arr,$style)
             {
                 $temp=0;
                 for($i=1;$i<count($arr);$i++)
                 {
                     for($j=0;$j<$i;$j++)
                     {
                         if($style=='bts') $op=$arr[$j]<$arr[$i];
                         else if($style=='stb') $op=$arr[$j]>$arr[$i];
                         if($op)
                         {
                             $temp=$arr[$j];
                             $arr[$j]=$arr[$i];
                             $arr[$i]=$temp;
                         }
                     }
                 }
                 foreach ($arr as $key => $value)
                 {
                     echo $value.',';   
                 }
             }
             $arr1=array(4,7,0,-7,1,14,5);
             insertSort($arr1,'bts');

<?php

$file = 'monkey.gif';

if (file_exists($file)) {

header('Content-Description: File Transfer');

header('Content-Type: application/octet-stream');

header('Content-Disposition: attachment; filename='.basename($file));

header('Content-Transfer-Encoding: binary');

header('Expires: 0');

header('Cache-Control: must-revalidate, post-check=0, pre-check=0');

header('Pragma: public');

header('Content-Length: ' . filesize($file));

ob_clean();

flush();

readfile($file);

exit;

}

?>

<?php

public function fddAction()

{

// get attachment location

$attachment_location = $_SERVER["DOCUMENT_ROOT"] . "/pdf/fdd/sample.pdf";

if (file_exists($attachment_location)) {

// attachment exists

// send open pdf dialog to user

header('Cache-Control: public'); // needed for i.e.

header('Content-Type: application/pdf');

header('Content-Disposition: inline; filename="sample.pdf"');

readfile($attachment_location);

die(); // stop execution of further script because we are only outputting the pdf

} else {

die('Error: File not found.');

}

}

?>

array("a","b","c","d","e","f","g")

$arr = array_slice($arr, 0, 3);

<?php
$arr = array("a"=>"a1","b"=>'b1',"c"=>"a2","d"=>"a1");
$arr1 = array_flip($arr);
print_r($arr1);//先反转一次,去掉重复值,输出Array ( [a1] => d [b1] => b [a2] => c )
$arr2 = array_flip($arr);
print_r($arr2);//再反转回来,得到去重后的数组,输出Array ( [a1] => d [b1] => b [a2] => c )
$arr3 = array_unique($arr);
print_r($arr3);//利用php的array_unique函数去重,输出Array ( [a] => a1 [b] => b1 [c] => a2 )
?>

<?php
$arr = array('a','b','c','d');
unset($arr[1]);
print_r($arr);
?>