HTML Forms & Multipart

With POST operations, 99% of the times the data is application/x-www-form-urlencoded which is the format you get from http_build_query. But, when you upload files (large data) you need multipart forms which are built for the big items. So, to upload files using HTML forms, you need to add enctype="multipart/form-data" to your form and use input="file" inputs.

To achieve this with cURL you need to set the file POSTFIELDS like this field => @file_path. But I never enjoy letting others encode my own shit. So I needed to take control here and create a function that can Multipart Encode to a string or a local file. Outputing to a string is good for small data but outputing to a file is good for large data that should not be handled in memory. As cURL accepts INFILE and INFILESIZE for the likes of POSTs and PUTs to send data from a file (not from memory) we can combine the two functions and make file uploads dead easy.

The next few lines will detail the encoding and later on I will publish my new cURL wrapper that is designed to upload / download large files and so on.

The Actual Script

See below the script doing the magic. It has 4-5 different function names doing same thing but I like to do this a lot. I get all those intuitive function names and easily remember them when writing code.

It uses el_files_getMIME if exists. Otherwise Content-Type is not added to encoded files.

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You can use like this to encode to a file. It returns the file path to the encoded data.

$post = array('note' => 'note1', 'upfile' => __FILE__);
$mp_file = el_http_mpEncode($post, $ctype, dirname(__FILE__).'/mpencoded.txt');
//$ctype returns the Content-Type you need to use

Or like this to encode to a string in memory. It returns ... a string.

$post = array('note' => 'note1', 'upfile' => __FILE__);
$mp_data = el_http_mpEncode($post, $ctype);
//$ctype returns the Content-Type you need to use

Very easy to use. If you add a filename as last parameter, you write everything to a file. Otherwise it returns encoded data as a string.

Testing It

Try it POSTing to http://cgi-lib.berkeley.edu/ex/fup.cgi from http://cgi-lib.berkeley.edu/ex/fup.html. The above array is created for this very FORM.