php man page for readfile

READFILE(3)								 1							       READFILE(3)

readfile - Outputs a file

SYNOPSIS
       int readfile (string  $filename, [bool  $use_include_path = false], [resource  $context])

DESCRIPTION
	Reads a file and writes it to the output buffer.

PARAMETERS
	      o $filename
		- The filename being read.

	      o $use_include_path
		- You can use the optional second parameter and set it to TRUE, if you want to search for the file in the include_path, too.

	      o $context
		- A context stream resource.

RETURN VALUES
	Returns  the number of bytes read from the file. If an error occurs, FALSE is returned and unless the function was called as @readfile(3),
       an error message is printed.

EXAMPLES
       Example #1

	      Forcing a download using readfile(3)

	      <?php
	      $file = 'monkey.gif';

	      if (file_exists($file)) {
		  header('Content-Description: File Transfer');
		  header('Content-Type: application/octet-stream');
		  header('Content-Disposition: attachment; filename='.basename($file));
		  header('Expires: 0');
		  header('Cache-Control: must-revalidate');
		  header('Pragma: public');
		  header('Content-Length: ' . filesize($file));
		  readfile($file);
		  exit;
	      }
	      ?>

	      The above example will output something similar to:[NOT DISPLAYABLE MEDIA]Open / Save dialogue

NOTES
       Note

	      readfile(3) 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(3).

       Tip

	      A  URL can be used as a filename with this function if the fopen wrappers have been enabled. See fopen(3) for more details on how to
	      specify the filename. See the "Supported Protocols and Wrappers" for links to information about what abilities the various  wrappers
	      have, notes on their usage, and information on any predefined variables they may provide.

       Note

	      Context support was added with PHP 5.0.0. For a description of contexts, refer to "Streams".

SEE ALSO
       fpassthru(3), file(3), fopen(3), include(3), require(3), virtual(3), file_get_contents(3), "Supported Protocols and Wrappers".

PHP Documentation Group 													       READFILE(3)