counter.php

<?php

/**
 * @file
 * Self-altering PHP counting script. Ideal for lambdas? 
 */
$count = 3;

$thisFile = fopen(__FILE__, 'r');
$thisFileContents = fread($thisFile, filesize(__FILE__));
$thisFileContents = str_replace('$count = ' . $count . ';', '$count = ' . ($count + 1). ';', $thisFileContents);
$thisFile = fopen(__FILE__, 'w');

fwrite($thisFile, $thisFileContents);
echo $count;