For the actual content, see:  http://mobiforge.com/developing/story/content-delivery-mobile-devices

But I must jot the solution down, as I spent a great deal of time struggling with setting headers and calling readfile($filename) with php to make ipod/iphone/ipad play/stream mp3, to no avail.

On a related note, I had to do header(“location: <url to mp3>”) as a workaround for the longest time, which is not ideal, because I want to track my mp3 downloads, i.e. my causing the redirect to the actual file location is no different than people accessing the file directly, and therefore there is no way for me to differentiate between me v.s. someone else, so I either 1. do not track, or 2. live in an infinite loop to call my tracking code (well, not infinite, since apache will fail/timeout).

Anyways, content from the aforementioned website:

Streaming for Apple iPhone

Apple iPhone uses HTTP byte-ranges for requesting audio and video files. First, the Safari Web Browser requests the content, and if it’s an audio or video file it opens it’s media player. The media player then requests the first 2 bytes of the content, to ensure that the Webserver supports byte-range requests. Then, if it supports them, the iPhone’s media player requests the rest of the content by byte-ranges and plays it.

Thomas Thomassen has done a great job on his PHP Resumable Download Server, providing working PHP code which supports byte-range downloads.

The following sample code is the complete version for the one from the first part of the article, but including byte-range support by using the rangeDownload() function when the $_SERVER['HTTP_RANGE'] header is present on the device’s HTTP request. The rangeDownload() function is an exact copy&paste from Thomas Thomassen’s code (only the relevant part).

<?php

if (is_file($file)) {

	header("Content-type: $mime_type");

	if (isset($_SERVER['HTTP_RANGE']))  { // do it for any device that supports byte-ranges not only iPhone

		rangeDownload($file);
	}
	else {

		header("Content-Length: ".filesize($file));
		readfile($file);
	}

else {

	// some error...

}

function rangeDownload($file) {

	$fp = @fopen($file, 'rb');

	$size   = filesize($file); // File size
	$length = $size;           // Content length
	$start  = 0;               // Start byte
	$end    = $size - 1;       // End byte
	// Now that we've gotten so far without errors we send the accept range header
	/* At the moment we only support single ranges.
	 * Multiple ranges requires some more work to ensure it works correctly
	 * and comply with the spesifications: http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html#sec19.2
	 *
	 * Multirange support annouces itself with:
	 * header('Accept-Ranges: bytes');
	 *
	 * Multirange content must be sent with multipart/byteranges mediatype,
	 * (mediatype = mimetype)
	 * as well as a boundry header to indicate the various chunks of data.
	 */
	header("Accept-Ranges: 0-$length");
	// header('Accept-Ranges: bytes');
	// multipart/byteranges
	// http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html#sec19.2
	if (isset($_SERVER['HTTP_RANGE'])) {

		$c_start = $start;
		$c_end   = $end;
		// Extract the range string
		list(, $range) = explode('=', $_SERVER['HTTP_RANGE'], 2);
		// Make sure the client hasn't sent us a multibyte range
		if (strpos($range, ',') !== false) {

			// (?) Shoud this be issued here, or should the first
			// range be used? Or should the header be ignored and
			// we output the whole content?
			header('HTTP/1.1 416 Requested Range Not Satisfiable');
			header("Content-Range: bytes $start-$end/$size");
			// (?) Echo some info to the client?
			exit;
		}
		// If the range starts with an '-' we start from the beginning
		// If not, we forward the file pointer
		// And make sure to get the end byte if spesified
		if ($range0 == '-') {

			// The n-number of the last bytes is requested
			$c_start = $size - substr($range, 1);
		}
		else {

			$range  = explode('-', $range);
			$c_start = $range[0];
			$c_end   = (isset($range[1]) && is_numeric($range[1])) ? $range[1] : $size;
		}
		/* Check the range and make sure it's treated according to the specs.
		 * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
		 */
		// End bytes can not be larger than $end.
		$c_end = ($c_end > $end) ? $end : $c_end;
		// Validate the requested range and return an error if it's not correct.
		if ($c_start > $c_end || $c_start > $size - 1 || $c_end >= $size) {

			header('HTTP/1.1 416 Requested Range Not Satisfiable');
			header("Content-Range: bytes $start-$end/$size");
			// (?) Echo some info to the client?
			exit;
		}
		$start  = $c_start;
		$end    = $c_end;
		$length = $end - $start + 1; // Calculate new content length
		fseek($fp, $start);
		header('HTTP/1.1 206 Partial Content');
	}
	// Notify the client the byte range we'll be outputting
	header("Content-Range: bytes $start-$end/$size");
	header("Content-Length: $length");

	// Start buffered download
	$buffer = 1024 * 8;
	while(!feof($fp) && ($p = ftell($fp)) <= $end) {

		if ($p + $buffer > $end) {

			// In case we're only outputtin a chunk, make sure we don't
			// read past the length
			$buffer = $end - $p + 1;
		}
		set_time_limit(0); // Reset time limit for big files
		echo fread($fp, $buffer);
		flush(); // Free up memory. Otherwise large files will trigger PHP's memory limit.
	}

	fclose($fp);

}
?>