File Management with PHP

We can find many articles related to uploading, viewing, and downloading files. This article is written on the basic concept of uploading and managing files. File uploading is the process of copying the file from your machine to the remote server. Other users of the same system then share this file by viewing or downloading it. What happens when you upload a file that already exists in the remote folder to which you are uploading?

While discussing this problem, other issues arise, such as: Should the program allow the user to restore this file or retain the existing file? If the file exists, then should I copy the file as a new version? How do I manage files, if the user uploads files of same name and type more than once?

Prerequisites
To understand this article, you should have a fair knowledge of PHP. To run examples given in your machine, you need Apache, PHP, and MySQL installed and configured.

Here’s what we want to accomplish:

  • When a user uploads a file for the first time, the system should upload the file in the specified folder and insert file details (file name, size, and type) in the database table.

  • When the user uploads a file for the second time (the filename has to be the same), the system will compare the size, date and time of the existing file and of the file being uploaded, and automatically assign a new version for the uploaded file if there is a difference. If there is no difference, then the existing file will be retained and a message will be displayed for the user.

  • A check box allows the user to replace the existing file. Clicking this option will replace the existing file. Note that only the latest version of the file can be replaced in this case, and not an older one.

  • The database will maintain file list and version details. Users should be able to view all the versions of a file and download the required version.

  • While displaying the file list, the program displays all the versions of files under one name. For example, if the file name is xyz.doc and its other versions are xyz_VERSION1.doc, xyz_VERSION2.doc, xyz_VERSION3.doc, and so on, the program will display the filename as xyz.doc for all the versions.

  • The program allows users to delete the file. Clicking on delete will ask for confirmation before proceeding.

{mospagebreak title=Building the Database}

Name the database “upload”. The database contains the table ‘file_manager’, which manages file information. The SQL statement for creating the table:

[code]
CREATE TABLE file_manager (
file_name varchar(50) default NULL,
file_type varchar(20) NOT NULL default '',
file_size varchar(20) NOT NULL default '',
file_modified varchar(20) NOT NULL default '',
file_parent_id mediumint(9) default NULL,
file_image_name varchar(50) default NULL,

 

KEY file_name (file_name),
KEY file_image_name (file_image_name)
) TYPE=MyISAM;
[/code]

File Management
I’ve written two programs to manage this file version. The first uploads the file (file_upload_manager.php), the second displays the file (file_upload_manager.php). The source code is tested on a Windows system.

NOTE:  Linux users, please change the folder path accordingly.

File Upload Manager:
This program displays a menu to select the file in your system, a check box and an Upload button. Once the user clicks the upload button, the program checks the file for existence, and undergoes a series of tests as described in the plan.

Now let’s look at the code snippets used in the program.

[code]
$dir_path Variable:
[/code]

This variable is the destination folder path.

[code]
$dir_path= "C:apachehtdocsfilemanager";
[/code]

This path is given for Windows-based systems. Please change your destination folder accordingly.

[code]
Get_New_File_Name() Function:
[/code]

This function is called from the main program when the program encounters files that exist and show a difference in size, date or time. This function will generate a new file name and return to the main function.

[code]
function Get_New_FIle_Name($file_name)
{
  $sqlQuery="SELECT  file_image_name FROM file_manager WHERE  file_name LIKE '$file_name%' AND  file_parent_id=1";

 

  $fResult=mysql_query($sqlQuery);
  $Last_Version=0;
  $ver=0;

 

  if(mysql_num_rows($fResult)){
      while($fRow=mysql_fetch_array($fResult)){         

 

list($junk,$ver)=explode("_VERSION",$fRow['file_image_name']);
         list($ver,$extn)=explode(".",$ver);
         $Last_Version = $Last_Version > $ver ? $Last_Version :

 

$ver;
       }
  }else{
      $new_file_name =$file_name."_VERSION".++$Last_Version;
      return $new_file_name;
  }

 

  if($Last_Version !=0){
      $new_file_name=$file_name."_VERSION".++$Last_Version;
      return $new_file_name;
  }
}
[/code]

The sql query in the beginning of the function will fetch file names of previous versions. If the sql query returns record sets, it means the file has previous versions. The while loop is executed to store the generated version number, and the value obtained is stored in $Last_Version. Otherwise, the new file name will be generated as file-name_VERSION1.

The next if statement checks for $Last_Version != 0, if true, $Last_Version is incremented by 1 and a new file name is assigned.

The return statement will return a new file name generated to the called statement.

{mospagebreak title=File_Size() and Display_form Functions}

File_Size() Function:
This function returns the file size in terms of Bytes, Kb or Mb.[code]<?
function File_Size($size)
{
    if($size > 104876){
        return $return_size=sprintf("%01.2f",$size / 1048576)."

 

Mb";
    }elseif($size > 1024){
        return $return_size=sprintf("%01.2f",$size / 1024)." Kb";
    }else{
        return $return_size=$size." Bytes";
    }
}
? >
[/code]

Display_form() Function:
This function is used to prompt the user to select the file from your local machine.

[code]
<?
function display_form($errMsg){
    global $dir_path; ? >

 

<html>
<head><title>File Manager</title></head>
<body bgcolor="#E5E5E5">
<div align="center">
<h4>File Manager</h4>

 

<? if($errMsg){
? ><font face="verdana, helvetica" size="2" color="red"><? echo $errMsg ? ></font>
<?
}
? >
<form action="<? echo $PHP_SELF; ? >"  enctype="multipart/form-data"

 

method="POST">
<table border="1">
<tr><th>File Location:</th><th><input type="file" name="up_file" /></th></tr>
<tr><th colspan="2"><br><input type="checkbox" name="replace" value="1">Replace Exiting File*</th></tr>
<tr><th colspan="2"><br><input type="submit" name="upload" value="Upload File !" /></th></tr>
</table>

 

<br>* - Clicking this option will replace the existing file
<br><a href="file_display_manager.php">File Manager</a>

 

<br><? if ($status){ echo "Result  :".$status;  }? >

 

<p><br><b>Folder Location:</b><? echo $dir_path ? >
<br>You can change this location by editing the file</font>

 

</form>
</div>
</body>
</html>
<? } ? >
[/code]

{mospagebreak title=The Main Program}

When you execute file_upload_manager.php, the code is executed first and the other functions described above are called in the middle of the program. Once the user selects the file and clicks upload, the main program part is executed. Here the program gets the upload file information like file size, file type, date modified and time stamp. Next it checks for the file existence in the destination folder. If the file is present the “if” part of the program gets executed, otherwise the file is copied to the destination folder and the file information is inserted in the database. If the file exists, and if the file size and/or time stamp differs, Get_New_File_Name() function is called to generate a new file name. Then the file is copied to the destination folder and the file information is stored in the database. If the file exists and the user had checked the “Replace Existing File” option, the file is replaced and the file information is updated in the database accordingly.

Otherwise, the user is redirected to the file_display_manager.php page and the message “A previous version of this file exists” is displayed.

File Display Manager:
This PHP script handles the displaying of files present in the folder. As described in the plan, the program will display the file name, size, type and an option to delete the file.

[code]
dir_display() Function:
[/code]

This function displays the files available in the folder in a table. The template looks like this:

File Manager

Size

Type Modified
abc.doc 25 Kb doc Oct 01, 2003 Delete
xyz.txt 24 bytes txt Oct 03, 2003 Delete
abc.doc 48 Kb doc Oct 05, 2003 Delete
abc.doc 67 Kb doc Nov 05, 2003 Delete
xyz.txt 58 bytes txt Oct 23, 2003 Delete


You can see that the file names are repeated, but you can see the file size and date modified differs. To view and/or download the file, you can click the hyperlink of the file name. This will show you the file name of the different version. You can customize the program to include another field “Version” to track the file version.

To delete a file, click on the ‘Delete’ hyperlink, which will prompt for confirmation.

I welcome your comments and suggestions!

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