Detailed explanation of php file upload and multiple file upload examples-PHP Tutorial-php.cn

In PHP program development, File upload is a very commonly used function and is also one of the necessary skills for PHP programmers. Fortunately, implementing the file upload function in PHP is much simpler than in languages such as Java and C#.

To use PHP to implement the file upload function, we first write two PHP files: index.php and upload.php. Among them, the index.php page is used to submit the form request for file upload, and the upload.php page is used to receive the uploaded file and process it accordingly.

First of all, let’s write a simple index.php file. Since it mainly involves html code, it is relatively simple, so we won’t go into details. The detailed code of the index.php page is as follows:

<?php
//设置编码为UTF-8，以避免中文乱码
header(&#39;Content-Type:text/html;charset=utf-8&#39;);
?>
<!DOCTYPE html>
<html>
<head>
  <title>文件上传表单页面</title>
</head>
<body>
<form action="upload.php" method="post" enctype="multipart/form-data">
文件1：<input name="upload_file1" type="file" /><br/>
文件2：<input name="upload_file2" type="file" /><br/>
<input type="submit" value="上传" />
</form>
</body>
</html>

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It is worth noting that since the HTTP protocol was originally designed, it did not support the file upload function. The default value of the encrypt attribute of the form form is application/x-www-form-urlencoded, which can only be used to submit general Form request. If the submitted form contains files that need to be uploaded, we need to change the enctype attribute value to multipart/form-data to implement the file upload function. In addition, the method attribute value must be post.

Next, we continue to write the code for the upload.php file.

<?php
//设置编码为UTF-8，以避免中文乱码
header(&#39;Content-Type:text/html;charset=utf-8&#39;);
$first_file = $_FILES[&#39;upload_file1&#39;]; //获取文件1的信息
$second_file = $_FILES[&#39;upload_file2&#39;]; //获取文件2的信息$upload_dir = &#39;D:/upload/&#39;;  //保存上传文件的目录//处理上传的文件1
if ($first_file[&#39;error&#39;] == UPLOAD_ERR_OK){
  //上传文件1在服务器上的临时存放路径
  $temp_name = $first_file[&#39;tmp_name&#39;];
  //上传文件1在客户端计算机上的真实名称
  $file_name = $first_file[&#39;name&#39;];
  //移动临时文件夹中的文件1到存放上传文件的目录，并重命名为真实名称
  move_uploaded_file($temp_name, $upload_dir.$file_name);
  echo &#39;[文件1]上传成功!<br/>&#39;;
}else{
  echo &#39;[文件1]上传失败!<br/>&#39;;
}

//处理上传的文件2
if ($second_file[&#39;error&#39;] == UPLOAD_ERR_OK){
  //上传文件2在服务器上的临时存放路径
  $temp_name = $second_file[&#39;tmp_name&#39;];
  //上传文件2在客户端计算机上的真实名称
  $file_name = $second_file[&#39;name&#39;];
  //移动临时文件夹中的文件2到存放上传文件的目录，并重命名为真实名称
  move_uploaded_file($temp_name, $upload_dir.$file_name);
  echo &#39;[文件2]上传成功!<br/>&#39;;
}else {
  echo &#39;[文件2]上传失败!<br/>&#39;;
}
?>

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In PHP, when the form request submitted by the browser client contains an uploaded file, PHP will temporarily store the uploaded file in a temporary directory (in Windows operating systems, the default The temporary directory is generally C:/Windows/Temp), and then the relevant information about the uploaded file is stored in the superglobal variable$_FILES. Therefore, we only need to obtain the uploaded file information through the $_FILES array, and then perform corresponding processing operations on it. Next, let’s take a look at the details of using the print_r() function to output the super global variable $_FILES when uploading two image files A.gif and B.gif through the browser:

Array ( [upload_file1] => Array ( 
 [name] => A.gif (客户端上传时的真实文件名称)
 [type] => image/gif (文件的类型)
 [tmp_name] => C:\Windows\Temp\php9803.tmp (文件上传到PHP服务器后临时存放的路径)
 [error] => 0 (错误信息，0表示没有错误)
 [size] => 87123 (文件大小，单位为字节)
 )
    [upload_file2] => Array (
 [name] => B.gif
 [type] => image/gif
 [tmp_name] => C:\Windows\Temp\php9813.tmp
 [error] => 0
 [size] => 93111
 )
)

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In the above example , the two file parameter names we uploaded are upload_file1 and upload_file2. Now, we let multiple files in the form use the same parameter name upload_file, and resubmit the two files just uploaded in the form of parameter arrays for upload. At this time, we need to modify the two file file fields in the index.php page to the following html code:

File 1:
##File 2:

In addition, we also need to upload.php page Make corresponding modifications:

<?php
//设置编码为UTF-8，以避免中文乱码
header(&#39;Content-Type:text/html;charset=utf-8&#39;);
$fileArray = $_FILES[&#39;upload_file&#39;];//获取多个文件的信息，注意：这里的键名不包含[]

$upload_dir = &#39;D:/upload/&#39;; //保存上传文件的目录
foreach ( $fileArray[&#39;error&#39;] as $key => $error) {
  if ( $error == UPLOAD_ERR_OK ) { //PHP常量UPLOAD_ERR_OK=0，表示上传没有出错
    $temp_name = $fileArray[&#39;tmp_name&#39;][$key];
    $file_name = $fileArray[&#39;name&#39;][$key];
    move_uploaded_file($temp_name, $upload_dir.$file_name);
    echo &#39;上传[文件&#39;.$key.&#39;]成功!<br/>&#39;;
  }else {
    echo &#39;上传[文件&#39;.$key.&#39;]失败!<br/>&#39;;
  }
}
?>

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Similarly, we use the print_r() function to view the details of the superglobal variable $_FILES in the above example:

Array ( 
 [upload_file] => Array ( 
 [name] => Array ( 
  [0] => A.gif
  [1] => B.gif  
  ) 
 [type] => Array ( 
  [0] => image/gif
  [1] => image/gif  
  ) 
 [tmp_name] => Array (
  [0] => C:\Windows\Temp\php87B9.tmp
  [1] => C:\Windows\Temp\php87BA.tmp
  ) 
 [error] => Array ( 
  [0] => 0
  [1] => 0  
  ) 
 [size] => Array ( 
  [0] => 87123
  [1] => 93111  
  )
 )
)

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Note 1: In PHP’s default Under the configuration, an error will occur if the uploaded file size exceeds a certain range. Please refer to the solution to the problem of how to modify the size limit of PHP uploaded files mentioned at the end of the article.

Remark 2: The above
Processing files The PHP code uploaded is just a simple introductory example and cannot be used directly as formal code because there are many security factors that require additional attention that have not been considered, such as: files type, file size, duplicate names of uploaded files, etc. Note 3: If the uploaded file name contains Chinese characters, it may cause the file name
garbled problem. At this time, you need to use the function iconv() to convert the encoding of the file name.

We learned earlier how to use PHP to implement file upload and multiple file upload. However, under the default configuration of PHP, when the uploaded file size exceeds a certain limit, we will get the following error message:

Warning: POST Content-Length of 625523488 bytes exceeds the limit of 8388608 bytes in Unknown on line 0
上述错误信息的大致意思是，我们使用POST请求提交的数据大小超过了服务器的最大限制数(8388608字节=8MB)。

出现上述错误的原因是，在PHP的配置文件php.ini中，默认存在如下配置信息(在php.ini中，行首的分号";"表示当前行是注释，不会生效)：

;脚本解析输入数据(类似 POST 和 GET)允许的最大时间，单位是秒。 它从接收所有数据到开始执行脚本进行测量的。 
max_input_time = 60

;允许客户端单个POST请求发送的最大数据
post_max_size = 8M

;是否开启文件上传功能
file_uploads = On

;文件上传的临时存放目录(如果不指定，使用系统默认的临时目录)
;upload_tmp_dir =

;允许单个请求上传的最大文件大小
upload_max_filesize = 2M

;允许单个POST请求同时上传的最大文件数量
max_file_uploads = 20

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From the above configuration information, we can see that PHP The default configuration information is the "culprit" that causes

PHP file upload to prompt that the file size exceeds the limit. The author has provided the Chinese annotation information corresponding to each command option in the above configuration information. You can modify the php.ini configuration file accordingly according to your actual needs.

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