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Keep your options open with FTP file uploads
Summary
A look at FTP-based file uploads using the PHP-FTP protocol to upload in a two-step process.
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With PHP, there's always more than one way to accomplish a particular task.
Take file upload, for example. Sure, you can do it the traditional way, using HTTP file upload and transferring the file directly to a location on your Web server's disk. Or you can do it the more exotic way, and use the FTP protocol to upload in a two-step process: from your local disk to a Web server, and then to an FTP server.
PHP supports both FTP and HTTP upload methods natively, leaving it to you to make the best decision based on the design requirements of your application. Transferring a file using PHP's FTP functions is almost the same as doing it using a traditional FTP client--as you'll see even the function names are similar to standard FTP commands.
Reams have already been written about HTTP file upload, which is why this brief tutorial focuses on FTP-based file uploads instead (in the example that follows, though, you'll see both in action). Note that this tutorial assumes that you have a working PHP/Apache installation, with both HTTP file upload and FTP functions active.
Step 1: Make sure you have permission to connect to/upload to the FTP server
PHP's FTP functions works over a client-server connection, and so you will need to log in to the target FTP server before you can perform a file upload. Your first task is to make sure that you have the credentials necessary for this action. This step might seem somewhat obvious, but you'd be surprised how many developers forget it and waste hours of debugging time later on.
You can check this by using a command-line FTP client to log in to the target FTP server and attempt to upload a dummy file (Listing A):
Listing A
$ ftp ftp> open some.host.com Connected to some.host.com. 220 Welcome to leon FTP Server! User: upload 331 User upload okay, need password. Password: *** 230 Restricted user logged in. ftp> bin 200 Type okay. ftp> hash Hash mark printing On ftp: (2048 bytes/hash mark) . ftp> put file.bin 200 PORT command successful. 150 Opening BINARY mode data connection. ## 226 Transfer completed. ftp: 4289 bytes sent in 0.00Seconds 4289000.00Kbytes/sec. ftp> bye 221 Goodbye.Once you've confirmed that you have the relevant access privileges, log out.
Step 2: Construct an upload form
Next, create a simple HTML form that asks the user for critical parameters--FTP server access information, the server directory to upload to, and the full path and name of the file to be uploaded. Here's a sample (Listing B) of what this form might look like:
Listing B
<html> <head></head> <body> <h2>Please provide the following information:</h2> <form enctype="multipart/form-data" method="post" action="upload.php"> <input type="hidden" name="MAX_FILE_SIZE" value="5000000" /> Host <br/> <input type="text" name="host" /><p /> Username <br /> <input type="text" name="user" /><p /> Password <br /> <input type="password" name="pass" /><p /> Destination directory <br /> <input type="text" name="dir" /><p /> File <br /> <input type="file" name="file" /><p /> <input type="submit" name="submit" value="Upload File" /> </form> </body> </html>Here, the <input type=file...> element renders as a file selection dialog box, from which the user can select the file to be uploaded. The <form enctype=...> element then forces the form data to be encoded as a multi-part submission, which makes it easier for PHP to identify the file component of the submission.
Step 3: Create the PHP upload processor
Once the form has been submitted to the Web server, the next (and final) step is to use PHP's FTP functions to transfer it to the target FTP server, using the access credentials supplied by the user. Here's the script (upload.php) that does all the work (Listing C):
Listing C
<?php
// get FTP access parameters
$host = $_POST['host'];
$user = $_POST['user'];
$pass = $_POST['pass'];
$destDir = $_POST['dir'];
$workDir = "/usr/local/temp"; // define this as per local system
// get temporary file name for the uploaded file
$tmpName = basename($_FILES['file']['tmp_name']);
// copy uploaded file into current directory
move_uploaded_file($_FILES['file']['tmp_name'], $workDir."/".$tmpName)
or die("Cannot move uploaded file to working directory");
// open connection
$conn = ftp_connect($host) or die ("Cannot initiate connection to
host");
// send access parameters
ftp_login($conn, $user, $pass) or die("Cannot login");
// perform file upload
$upload = ftp_put($conn, $destDir."/".$_FILES['file']['name'],
$workDir."/".$tmpName, FTP_BINARY);
// check upload status
// display message
if (!$upload) {
echo "Cannot upload";
} else {
echo "Upload complete";
}
// close the FTP stream
ftp_close($conn);
// delete local copy of uploaded file
unlink($workDir."/".$tmpName) or die("Cannot delete uploaded
file from working directory -- manual deletion recommended");
?>
This might appear complicated, but it's actually fairly straightforward. Here's what's happening:
1- Once the form has been submitted, the credentials supplied by the user in the various form input fields are extracted into regular PHP variables. Information about the uploaded file also now becomes available through PHP's special $_FILES array.
2- The $_FILES array is made up of multiple sub-arrays, one for each uploaded file. The keys of each sub-array hold information about the size, MIME type, original name and temporary name of the corresponding uploaded file. This information is used by the move_uploaded_file() function to transfer the file from the system's temporary directory to the working directory. Remember to alter the value of $workDir to reflect a valid file path on your system.
3- The ftp_connect() and ftp_login() functions are used to initiate a connection to the named FTP host, and log in to it using the supplied credentials.
4- Assuming a successful login, the ftp_put() function is used to upload the file from the working directory to the remote directory specified by the user and rename it to its original form. Note the addition of the special FTP_BINARY argument to ftp_put(), to specify that the file be transferred in binary (not ASCII) mode. Depending on the result code returned by the ftp_put() function, an error or success message is displayed to the user.
5- The ftp_close() function is used to end the FTP session, and the unlink() function is used to clean up by deleting the local copy of the file that was created in step (2).
Simple, isn't it? Go on, try it out for yourself and see!
Talkback
Keep your options open with FTP file uploads
I have a customer that needs to have a file submission/upload form on their website. The thing is that they have 2 servers - One is the hosting ftp and the other in a in-house network ftp. They want the form on the website server to upload the files to the in-house ftp. This is out of my expertise and I need help. I have been looking for a third party script/application that would allow me to do all of this. Can you point me in the right direction? Any help would be greatly appreciated! - Thanks
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Excellent article.
Not to put too much demand on free advice, but what would be *really* swell is a method to use the HTTP file upload facility to initial transfer of the file *directly* to another server than the local one providing the input form.
That would avoid double-transfer of the file and thus avoid huge delays when the local server has limited network bandwidth and the ultimate target server has lots. (I am facing this problem now with huge MPEG files that must be transferred.)
Is there some way accomplish this kind of voodoo?