Upload a file using file_get_contents

Question

I realise I can do this with CURL very easily, but I was wondering if it was possible to use file_get_contents() with the http stream context to upload a file to a remote web server, and if so, how?

Answer 1

First of all, the first rule of multipart Content-Type is to define a boundary that will be used as a delimiter between each part (because as the name says, it can have multiple parts). The boundary can be any string that is not contained in the content body. I will usually use a timestamp:

define('MULTIPART_BOUNDARY', '--------------------------'.microtime(true)); 

Once your boundary is defined, you must send it with the Content-Type header to tell the webserver what delimiter to expect:

$header = 'Content-Type: multipart/form-data; boundary='.MULTIPART_BOUNDARY; 

Once that is done, you must build a proper content body that matches the HTTP specification and the header you sent. As you know, when POSTing a file from a form, you will usually have a form field name. We'll define it:

// equivalent to <input type="file" name="uploaded_file"/> define('FORM_FIELD', 'uploaded_file');  

Then we build the content body:

$filename = "/path/to/uploaded/file.zip"; $file_contents = file_get_contents($filename);      $content =  "--".MULTIPART_BOUNDARY."\r\n".             "Content-Disposition: form-data; name=\"".FORM_FIELD."\"; filename=\"".basename($filename)."\"\r\n".             "Content-Type: application/zip\r\n\r\n".             $file_contents."\r\n";  // add some POST fields to the request too: $_POST['foo'] = 'bar' $content .= "--".MULTIPART_BOUNDARY."\r\n".             "Content-Disposition: form-data; name=\"foo\"\r\n\r\n".             "bar\r\n";  // signal end of request (note the trailing "--") $content .= "--".MULTIPART_BOUNDARY."--\r\n"; 

As you can see, we're sending the Content-Disposition header with the form-data disposition, along with the name parameter (the form field name) and the filename parameter (the original filename). It is also important to send the Content-Type header with the proper MIME type, if you want to correctly populate the $_FILES[]['type'] thingy.

If you had multiple files to upload, you just repeat the process with the $content bit, with of course, a different FORM_FIELD for each file.

Now, build the context:

$context = stream_context_create(array(     'http' => array(           'method' => 'POST',           'header' => $header,           'content' => $content,     ) )); 

And execute:

file_get_contents('http://url/to/upload/handler', false, $context); 

NOTE: There is no need to encode your binary file before sending it. HTTP can handle binary just fine.