<?php

$empty = false; $t = microtime(1); for ($i = 0; $i < 100000000; $i++) if(empty($empty));echo microtime(1) - $t; echo " - ", (int) $empty, "\n";
$empty = true; $t = microtime(1); for ($i = 0; $i < 100000000; $i++) if(empty($empty));echo microtime(1) - $t; echo " - ", (int) $empty, "\n";
$empty = false; $t = microtime(1); for ($i = 0; $i < 100000000; $i++) if(!empty($empty));echo microtime(1) - $t; echo " - !", (int) $empty, "\n";
$empty = true; $t = microtime(1); for ($i = 0; $i < 100000000; $i++) if(!empty($empty));echo microtime(1) - $t; echo " - !", (int) $empty, "\n";


?>
3.4707100391388 - 0
3.1234660148621 - 1
3.9550409317017 - 0
4.4936611652374 - 1