On 30/01/2015 18:42, Robert Williams wrote:
% php -r '$e="0";for($i=0;$i<2500;$i++){$e="0$e";} gethostbyname($e);’
What’s not being discussed is how it works. From the naive viewpoint of a PHP
end-user, I’d expect this one-liner to have the same effect:
% php -r '$e="0$e"; gethostbyname($e);’
But it doesn’t. Can someone familiar with PHP’s internals explain why this code
triggers the overflow, and whether it will actually do so reliably?
No need to be familiar with the internals, you just need to unroll the
loop properly in your head:
initialise: $e = "0"; => "0"
$i=0: $e = "0$e"; => "0" . "0" => "00"
$i=1: $e = "0$e"; => "0" . "00" => "000"
and so on until you have 2501 zeroes when $i=2499
As Patrick points out, this is a really weird way of initialising that
variable, and is presumably translated from another language by someone
who doesn't know PHP.
--
Rowan Collins
[IMSoP]
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: http://www.php.net/unsub.php
