ループ対決
<form action="">
<input type="text" name="a" size="5"> 回
<input type="submit" value=" Go "></form>
<?
function get(){ 
    list($usec, $sec) = explode(" ",microtime()); 
    return ((float)$sec + (float)$usec); 
    }
$a = $_REQUEST['a'];
if(!$a) $a="100";
echo "$a 回loop<p><tt>";

$st1=get();
for($i=0; $i<$a; $i++);
$out1=get()-$st1;
echo "for__ $out1 s<br>";

$st2=get();
while($j<$a){$j++;}
$out2=get()-$st2;
echo "while $out2 s</tt>";

?> 
<p>せいぜい300万回まで