FTP hosting is often much cheaper than regular web hosting. The upload with an ftp client is for sure the most common way, but could be a problem for people behind a firewall or without enough rights (capabilities) to install a FTP client. For those a upload via a web form is the best solution.

Upload limitations by your web server
The default value for file uploads within PHP is 2MB, if you need to upload bigger files you need to change your PHP configuration or need to create a .htaccess file with this code to upload files of max. 16MB:

php_value upload_max_filesize 16M
php_value post_max_size 20M

The value for the post_max_size is larger than the value for the upload_max_size because we want to be able to upload more than just a file (also other data via text fields or text areas). The .htaccess file needs to be in the same directory than your PHP upload script.
Using cURL for file transmissions
cURL is a great library for file transmissions via different types of protocols. The library supports the transport via POST, GET, FTP upload and much more. cURL is also able to authenticate on the target server or website.

In this tutorial we want to upload a file to some (password protected) remote FTP server via a web form.

Select file

Next we need some PHP code to handle the upload and opens a stream to send the file via cURL to the remote FTP server (place this code above the html code):

if (isset($_POST['Submit'])) {

 if (!empty($_FILES['upload']['name'])) {

 	$ch = curl_init();

 	$localfile = $_FILES['upload']['tmp_name'];

 	$fp = fopen($localfile, 'r');

 	curl_setopt($ch, CURLOPT_URL, 'ftp://ftp_login:password@ftp.domain.com/'.$_FILES['upload']['name']);

 	curl_setopt($ch, CURLOPT_UPLOAD, 1);

 	curl_setopt($ch, CURLOPT_INFILE, $fp);

 	curl_setopt($ch, CURLOPT_INFILESIZE, filesize($localfile));

 	curl_exec ($ch);

 	$error_no = curl_errno($ch);

 	curl_close ($ch);

        if ($error_no == 0) {

        	$error = 'File uploaded succesfully.';

        } else {

        	$error = 'File upload error.';

        }

 } else {

    	$error = 'Please select a file.';

 }

}

This small PHP snippet is responsible for the upload to some remote FTP server. We suggest using more validation routines in a production environment.