php基础知识(5)－文件下传
php基础知识(5)－文件上传
php基础知识－文件上传
示例代码下载页http://xieye.iteye.com/blog/1336095
可以使用户上传文本和二进制文件。用 PHP 的认证和文件操作函数，可以完全控制允许哪些人上传以及文件上传后怎样处理。
相关的设置: 请参阅 php.ini 的 file_uploads，upload_max_filesize，upload_tmp_dirpost_max_size 以及 max_input_time 设置选项
默认情况下，php的配置允许上传，而且文件大小不能超过2M。
php上传需要构建特殊表单，其实就是表单多了一个属性 enctype="multipart/form-data"，还有表单元素中多了一个file元素。
在服务端需要使用move_uploaded_file 函数，并有一个$_FILE超全局变量可用。
以下抄自php手册
$_FILES['userfile']['name']
客户端机器文件的原名称。
$_FILES['userfile']['type']
文件的 MIME 类型，如果浏览器提供此信息的话。一个例子是“image/gif”。不过此 MIME 类型在 PHP 端并不检查，因此不要想当然认为有这个值。
$_FILES['userfile']['size']
已上传文件的大小，单位为字节。
$_FILES['userfile']['tmp_name']
文件被上传后在服务端储存的临时文件名。
$_FILES['userfile']['error']
和该文件上传相关的错误代码。此项目是在 PHP 4.2.0 版本中增加的。
>>>
建议1：实际应用中用户上传的文件不应与程序放在同一目录（那是个糟糕的习惯），本教程为简单起见放到了一起。
建议2：为系统安全，总是应该给上传文件重命名，如需保存原文件名，可以保存到数据库。
建议3：如果用户经常会上传文件，则应该在某个目录下建子目录，如uploadfile目录下有20120102，20120103等按天的目录，
用户上传的文件按天存放在各自的目录中。
建议4：不建议把上传文件按内容存放于各自的文件夹，除非文件少。因为同一目录下有太多文件时（比如超过10000个），系统检索速度会变慢
，无论linux还是windows。
建议5：如果建了子目录，通常需要把路径也存放于数据库中。
例子1：
http://localhost/command/peixun/upload/1.php
普通的上传文件的代码，上传完之后可以到文件夹中检查一下是否真的上传了。
例子2
参考来源；http://www.phpletter.com/Our-Projects/AjaxFileUpload/
使用了jquery库和一个jquery插件ajaxfileupload
测试url
http://localhost/command/peixun/upload/2.php
用js来上传文件，客户端代码变了，但服务端代码完全不变。
代码可下载
1.php
<?php //第一个例子
require_once('../Public/CommandLine.php');
$isget = ($_SERVER['REQUEST_METHOD'] == 'GET') ? 1 : 0;
if ($isget) {
$html = <<<longs
<html>
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