How to output a massive file with PHP without running out of memory

Question

I have the code below to output a big file, but it's falling over because PHP's memory use seems to grow and grow as the file is read:

  <?php
  // various header() calls etc.
  $stream = fopen($tarfile,'r');
  ob_end_flush();
  while (!feof($stream)) {
    $buf = fread($stream, 4096);
    print $buf;
    flush();
    unset($buf);
    $aa_usage = memory_get_usage(TRUE); // ← this keeps going up!
  }
  fclose($stream);

I had thought that by the combination of flush and unset the additional memory use would be limited to the 4k buffer, but I'm clearly wrong.

Answer 1

If all you need is to output the content of a file then the right tool to do it is the PHP function readfile(). Replace all the code you posted with:

readfile($tarfile);

As the documentation says:

Note:

readfile() will not present any memory issues, even when sending large files, on its own. If you encounter an out of memory error ensure that output buffering is off with ob_get_level().