Setting the header to be content image in CakePHP - cakephp

Question

I am writing an action in a controller where in a certain case, I want to output raw image data directly, and want to set the header content-type appropriate. However I think the header is already being set earlier by CakePHP (I am setting render to be false).
Is there a way to get around this? Thanks!

Answer 1

As said before, CakePHP does not send headers when render is false. Beware though, that any code doing an 'echo' will send headers (except you are using output-buffering). This includes messages from PHP (warnings etc.).
Sending the file can be done in numerous ways, but there are two basic ways:
Send the file using plain PHP
function send_file_using_plain_php($filename) {
// Avoids hard to understand error-messages
if (!file_exists($filename)) {
throw RuntimeException("File $filename not found");
}
$fileinfo = new finfo(FILEINFO_MIME);
$mime_type = $fileinfo->file($filename);
// The function above also returns the charset, if you don't want that:
$mime_type = reset(explode(";", $mime_type));
// gets last element of an array
header("Content-Type: $mime_type");
header("Content-Length: ".filesize($filename));
readfile($filename);
}
Use X-Sendfile and have the Webserver serve the file
// This was only tested with nginx
function send_file_using_x_sendfile($filename) {
// Avoids hard to understand error-messages
if (!file_exists($filename)) {
throw RuntimeException("File $filename not found");
}
$fileinfo = new finfo(FILEINFO_MIME);
$mime_type = $fileinfo->file($filename);
// The function above also returns the charset, if you don't want that:
$mime_type = reset(explode(";", $mime_type));
// gets last element of an array
header("Content-Type: $mime_type");
// The slash makes it absolute (to the document root of your server)
// For apache and lighttp use:
header("X-Sendfile: /$filename");
// or for nginx: header("X-Accel-Redirect: /$filename");
}
The first function occupies one PHP-process / thread while the data is being send and supports no Range-Requests or other advanced HTTP-features. This should therefore only be used with small files, or on very small sites.
Using X-Sendfile you get all that, but you need to know which webserver is running and maybe even a change to the configuration is needed. Especially when using lighttp or nginx this really pays off performance-wise, because these webservers are extremly good at serving static files from disk.
Both functions support files not in the document-root of the webserver. In nginx there are so called "internal locations" (http://wiki.nginx.org/HttpCoreModule#internal). These can be used with the X-Accel-Redirect-Header. Even rate-throtteling is possible, have a look at http://wiki.nginx.org/XSendfile.
If you use apache, there is mod_xsendfile, which implements the feature needed by the second function.

Answer 2

It's not $this->render(false), it's $this->autoRender=false; The header is not sent in the controller action unless you echo something out.

Answer 3

If render is false, cake will not send a header.
You can rely on plain ol' php here.
PNG:
header('Content-Type: image/gif');
readfile('path/to/myimage.gif');
JPEG:
header('Content-Type: image/jpeg');
readfile('path/to/myimage.jpg');
PNG:
header('Content-Type: image/png');
readfile('path/to/myimage.png');