- memory_get_peak_usage: documentation ( source)
- str_repeat: documentation ( source)
<?php
echo memory_get_peak_usage()/(1024*1024) . 'MB', "\n";
$pass = str_repeat('a', 1024 * 1024 * 2);
$pass . $pass;
echo memory_get_peak_usage()/(1024*1024) . 'MB';