PHP readfile memory usage test

<?php

if (!file_exists('foo.dat')) {
    /* If the file to be read from disk doesn't exist create it */
    file_put_contents('foo.dat', str_repeat(0x00,1024*1024*10));
}

if (ini_get('output_buffering')) die('Please turn off output buffering...');
$mem_start = memory_get_usage(); /* Store the memory usage here */

readfile('foo.dat'); /* Read the file into output */
$mem_end = memory_get_usage(); /* Store the memory usage here */
$mem_peak = memory_get_peak_usage();
echo "<pre>Memory started at: $mem_start\nMemory ended at: $mem_end\nMemory peaked at: $mem_peak</pre>";

?>