PHP File Upload

With PHP, it is possible to upload files to the server.

Create an Upload-File Form

To allow users to upload files from a form can be very useful.

Look at the following HTML form for uploading files:

<html>

<body>

<form action="upload_file.php" method="post"

enctype="multipart/form-data">

<label for="file">Filename:</label>

<input type="file" name="file" id="file" />

<br />

<input type="submit" name="submit" value="Submit" />

</form>

</body>

</html>

Notice the following about the HTML form above:

The enctype attribute of the <form> tag specifies which content-type to use when submitting the form. "multipart/form-data" is used when a form requires binary data, like the contents of a file, to be uploaded
The type="file" attribute of the <input> tag specifies that the input should be pocessed as a file. For example, when viewed in a browser, there will be a browse-button next to the input field

Note: Allowing users to upload files is a big security risk. Only permit trusted users to perform file uploads.

The "upload_file.php" file contains the code for uploading a file:

<?php

if ($_FILES["file"]["error"] > 0)

  echo "Error: " . $_FILES["file"]["error"] . "<br />";

else

  echo "Upload: " . $_FILES["file"]["name"] . "<br />";

  echo "Type: " . $_FILES["file"]["type"] . "<br />";

  echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";

  echo "Stored in: " . $_FILES["file"]["tmp_name"];

?>

By using the global PHP $_FILES array you can upload files from a client computer to the remote server.

The first parameter is the form's input name and the second index can be either "name", "type", "size", "tmp_name" or "error". Like this:

$_FILES["file"]["name"] - the name of the uploaded file
$_FILES["file"]["type"] - the type of the uploaded file
$_FILES["file"]["size"] - the size in bytes of the uploaded file
$_FILES["file"]["tmp_name"] - the name of the temporary copy of the file stored on the server
$_FILES["file"]["error"] - the error code resulting from the file upload

This is a very simple way of uploading files. For security reasons, you should add restrictions on what the user is allowed to upload.

In this script we add some restrictions to the file upload. The user may only upload .gif or .jpeg files and the file size must be under 20 kb:

<?php

if ((($_FILES["file"]["type"] == "image/gif")

|| ($_FILES["file"]["type"] == "image/pjpeg"))

&& ($_FILES["file"]["size"] < 20000))

  if ($_FILES["file"]["error"] > 0)

    echo "Error: " . $_FILES["file"]["error"] . "<br />";

  else

    echo "Upload: " . $_FILES["file"]["name"] . "<br />";

    echo "Type: " . $_FILES["file"]["type"] . "<br />";

    echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";

    echo "Stored in: " . $_FILES["file"]["tmp_name"];

else

  echo "Invalid file";

?>

The examples above create a temporary copy of the uploaded files in the PHP temp folder on the server.

The temporary copied files disappears when the script ends. To store the uploaded file we need to copy it to a different location:

<?php

if (($_FILES["file"]["type"] == "image/gif")

|| ($_FILES["file"]["type"] == "image/pjpeg")

&& ($_FILES["file"]["size"] < 20000))

  if ($_FILES["file"]["error"] > 0)

    echo "Return Code: " . $_FILES["file"]["error"] . "<br />";

  else

    echo "Upload: " . $_FILES["file"]["name"] . "<br />";

    echo "Type: " . $_FILES["file"]["type"] . "<br />";

    echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";

    echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";

    if (file_exists("upload/" . $_FILES["file"]["name"]))

      echo $_FILES["file"]["name"] . " already exists. ";

    else

      move_uploaded_file($_FILES["file"]["tmp_name"],

      "upload/" . $_FILES["file"]["name"]);

      echo "Stored in: " . "upload/" . $_FILES["file"]["name"];

else

  echo "Invalid file";

?>

The script above checks if the file already exists, if it does not, it copies the file to the specified folder.

Note: This example saves the file to a new folder called "upload"