PHP: Sending Motion-JPEG

As you may know from past posts, I was trying to send Motion-JPEG from a PHP script. This proved (for many reason) not so easy. After I conquered writing php extension modules, I was still left with nuances in PHP that made it difficult to send MJPEG from my script.

Here's the basic run-down of difficulties:

• PHP buffers output to the client and this keeps you from doing continuous streams of data easily
• PHP doesn't allow you to send headers after it thinks the headers have already been sent
• Apache has some other handlers that also cause buffering
• Apache does some client negotiation that conflicts with MJPEG (mod_gzip)

Searching the Eentarnets did not produce good results on how to handle this. At least, not in a single place and easily findable. So here's my solution for others to use:

<?
# Used to separate multipart
$boundary = "my_mjpeg";

# We start with the standard headers. PHP allows us this much
header("Cache-Control: no-cache");
header("Cache-Control: private");
header("Pragma: no-cache");
header("Content-type: multipart/x-mixed-replace; boundary=$boundary");

# From here out, we no longer expect to be able to use the header() function
print "--$boundary\n";

# Set this so PHP doesn't timeout during a long stream
set_time_limit(0);

# Disable Apache and PHP's compression of output to the client
@apache_setenv('no-gzip', 1);
@ini_set('zlib.output_compression', 0);

# Set implicit flush, and flush all current buffers
@ini_set('implicit_flush', 1);
for ($i = 0; $i < ob_get_level(); $i++)
    ob_end_flush();
ob_implicit_flush(1);

# The loop, producing one jpeg frame per iteration
while (true) {
    # Per-image header, note the two new-lines
    print "Content-type: image/jpeg\n\n";

    # Your function to get one jpeg image
    print get_one_jpeg();

    # The separator
    print "--$boundary\n";
}
?>

That's it in a nutshell. Make sure that your PHP script does not contain any newlines or data before or after the PHP enclosures (<? ... ?>).