PHP single file and multiple file upload examples explained

This article gives you a detailed analysis of the code and problem solutions for single file upload and multi-file upload in PHP. Let’s learn and refer to it together.

$_FILES When is an empty array?

When the form submission enctype is not equal to multipart/form-data in the php.ini configuration file, file_uploads = Off and the uploaded file size > the maximum upload size configured in the php.ini configuration file

As long as $_FILES is an empty array, the above problems may occur and must be fixed!

If you click the "Upload Button" immediately without selecting any file, $_FILES will be an array with elements. Each attribute in the element is an empty string, and the error attribute is 4

Single file upload

##$_FILES data structure

array(
  'filename' => array(
    'name' => 'xxx.png',
    'type' => 'image/png',
    'size' => 2548863,
    'tmp_name' => '/img/sdsdsd.png',
    'error' => 0
  )
)

Whether it is

Single file or Multiple file upload, there will be 5 fixed attributes: name / size / type / tmp_name / error

Multiple file upload

Compared with single file upload, multi-file upload is much more complicated to process. The two forms of multi-file upload on the front end

//name相同
<form method="post" enctype="multipart/form-data">
  <input type="file" name="wt[]"/>
  <input type="file" name="wt[]"/>
  <input type="submit" value="提交"/>
</form>

//name不同（简单点）
<form method="post" enctype="multipart/form-data">
  <input type="file" name="wt"/>
  <input type="file" name="mmt"/>
  <input type="submit" value="提交"/>
</form>

The back-end

$_FILES corresponds to different data structures

//name相同
array (size=1)
 'wt' => 
  array (size=5)
   'name' => 
    array (size=2)
     0 => string '新建文本文档 (2).txt' (length=26)
     1 => string '新建文本文档.txt' (length=22)
   'type' => 
    array (size=2)
     0 => string 'text/plain' (length=10)
     1 => string 'text/plain' (length=10)
   'tmp_name' => 
    array (size=2)
     0 => string 'C:\Windows\php1D64.tmp' (length=22)
     1 => string 'C:\Windows\php1D65.tmp' (length=22)
   'error' => 
    array (size=2)
     0 => int 0
     1 => int 0
   'size' => 
    array (size=2)
     0 => int 0
     1 => int 1820

//name不同（简单点）
array (size=2)
 'wt' => 
  array (size=5)
   'name' => string '新建文本文档 (2).txt' (length=26)
   'type' => string 'text/plain' (length=10)
   'tmp_name' => string 'C:\Windows\php39C7.tmp' (length=22)
   'error' => int 0
   'size' => int 0
 'mmt' => 
  array (size=5)
   'name' => string '新建文本文档.txt' (length=22)
   'type' => string 'text/plain' (length=10)
   'tmp_name' => string 'C:\Windows\php39D8.tmp' (length=22)
   'error' => int 0
   'size' => int 1820

Field Error purpose

Value: 1 The uploaded file exceeds the value limited by the upload_max_filesize option in php.ini.

Value: 2 The size of the uploaded file exceeds the value specified by the MAX_FILE_SIZE option in the HTML form.

Value: 3 The file was only partially uploaded.

Value: 4 No files were uploaded. Value: 5 The upload file size is 0.

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