php5 - Creating a file upload form with PHP

Hi,
Now we can create our upload.php file. To start we'll check that the file upload is safe by setting a list of allowed filetypes and disallowing all other file uploads. This will prevent people from uploading malicious files. Then we will check the filesize to prevent large files from being uploaded.

<?php
// Configuration - Your Options
$allowed_filetypes = array('.jpg','.gif','.bmp','.png'); // These will be the types of file that will pass the validation.
$max_filesize = 524288; // Maximum filesize in BYTES (currently 0.5MB).
$upload_path = './files/'; // The place the files will be uploaded to (currently a 'files' directory).

$filename = $_FILES['userfile']['name']; // Get the name of the file (including file extension).
$ext = substr($filename, strpos($filename,'.'), strlen($filename)-1); // Get the extension from the filename.

// Check if the filetype is allowed, if not DIE and inform the user.
if(!in_array($ext,$allowed_filetypes))
die('The file you attempted to upload is not allowed.');

// Now check the filesize, if it is too large then DIE and inform the user.
if(filesize($_FILES['userfile']['tmp_name']) > $max_filesize)
die('The file you attempted to upload is too large.');

// Check if we can upload to the specified path, if not DIE and inform the user.
if(!is_writable($upload_path))
die('You cannot upload to the specified directory, please CHMOD it to 777.');

// We'll start handling the upload in the next step

?>

It's worth noting, that by default PHP will not handle file uploads larger than 2MB, if you require PHP to handle larger files then you must first set upload_max_filesize and post_max_size in your php.ini file to be larger than 2MB.
Now that we know we have a suitably small file of a safe filetype we can upload it to where we want it to go. Using the same file:

<?php
// Configuration - Your Options
$allowed_filetypes = array('.jpg','.gif','.bmp','.png'); // These will be the types of file that will pass the validation.
$max_filesize = 524288; // Maximum filesize in BYTES (currently 0.5MB).
$upload_path = './files/'; // The place the files will be uploaded to (currently a 'files' directory).

$filename = $_FILES['userfile']['name']; // Get the name of the file (including file extension).
$ext = substr($filename, strpos($filename,'.'), strlen($filename)-1); // Get the extension from the filename.

// Check if the filetype is allowed, if not DIE and inform the user.
if(!in_array($ext,$allowed_filetypes))
die('The file you attempted to upload is not allowed.');

// Now check the filesize, if it is too large then DIE and inform the user.
if(filesize($_FILES['userfile']['tmp_name']) > $max_filesize)
die('The file you attempted to upload is too large.');

// Check if we can upload to the specified path, if not DIE and inform the user.
if(!is_writable($upload_path))
die('You cannot upload to the specified directory, please CHMOD it to 777.');

// Upload the file to your specified path.
if(move_uploaded_file($_FILES['userfile']['tmp_name'],$upload_path . $filename))
echo 'Your file upload was successful, view the file <a href="' . $upload_path . $filename . '" title="Your File">here</a>'; // It worked.
else
echo 'There was an error during the file upload. Please try again.'; // It failed .

?>

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Thanks & regards
Lokananth
Live Chat Software By miOOt

This is a tissue paper security check. sneeze on it and you can break it.
extensions can be changed or completely left off. any basic hacker can work around this simple check. maybe use a function in the GD lib to check it first... maybe something like exif-imagetype or just getimagesize