Valid IP in php

I've been trying to determine if a string coming from an html form is a valid IP address, I tried using the regexp's functions, but I can't hit the clown yet, so I'm asking you out if you can give me a hand on here.

I've split the string on 4 strings more separated by ".", then determine if each of those is a number, but... what if the user enters just letters??

Some help would be appreceiated... URL

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Bigotes :{

A regex solution might be an idea but I'd hate to tackle it since the range is not easy to deal with. I see this as four steps:

1) break up the elements
2) verify number of elements=4
3) verify all integers
4) verify valid range

to wit:
$invalid=0;
$levels=explode('.',$ip);
if (count($levels)!=4) $invalid='true';
for ($i=0;$i<4;$i++)
{
if ($levels[$i]!=intval($levels[$i]) $invalid='true';
if ($levels[$i]<0 OR $levels[$i]>256) $invalid='true';
}

if ($invalid)
{
// $ip not a valid ip address
}else
{
// $ip valid
}

Technically some values of $ip would not be valid that would slip thru, but this should be good enough for most applications.

HTH

Rod

I use:

<BLOCKQUOTE><font size="1" face="Verdana,Arial,Helvetica">code:</font><HR><pre>
if (ereg("[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}",$ip)) {
print "The IP is valid.";
}
else {
print("The IP is not valid.");
}
[/code]

If you want to check everything you could make sure its not part of the 10.* A class or the 192.168.* B class since those are reserved for private networks.

N.