[RESOLVED] Regex and IP addresses

[badgoat]

Hello!

Thanks to another user here who directed me to a book and a site which explains regular expressions (I didn't even know that was the term I needed!) I have been using regex for form validation. I have run into a problem when trying to validate an IP address field. Using the code below, I am allowed to enter an octet of 256, and I am not sure what I did wrong. Is anyone able to easily see what's wrong?

if (!preg_match('/(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/', $string)) {

} else {

}

[laserlight]

You are probably missing the assert start and end meta-characters.

/^{...pattern...$/}

[badgoat]

I simplified it and with the change which Laserlight recommended, here's what is currently working:

if (!preg_match('/^([0-2][0-5][0-5]|[0-9][0-9]|[0-9])\\.([0-2][0-9][0-9]|[0-9][0-9]|[0-9])\\.([0-2][0-9][0-9]|[0-9][0-9]|[0-9])\\.([0-2][0-9][0-9]|[0-9][0-9]|[0-9])/', $ip)){
die("The format of the external IP address is incorrect!  Press the BACK button and edit the external IP address.");
}
else
{

Thanks Laserlight!

[laserlight]

Your simplification introduced a bug, methinks. Try testing with 199.1.1.1 or 1.299.1.1

[badgoat]

Aah! You're right.. Tiny bit more tweaking and it'll be ok!

edit

if (!preg_match('/^{([0-2][0-5][0-5]|[0-1][0-9][0-9]|[0-9][0-9]|[0-9])\.([0-2][0-5][0-5]|[0-1][0-9][0-9]|[0-9][0-9]|[0-9])\.([0-2][0-5][0-5]|[0-1][0-9][0-9]|[0-9][0-9]|[0-9])\.([0-2][0-5][0-5]|[0-1][0-9][0-9]|[0-9][0-9]|[0-9])/',} $ip)){
die("The format of the external IP address is incorrect! Press the BACK button and edit the external IP address.");
}
else
{

[laserlight]

I suggest that you use this regex pattern:

/^((1?\d{1,2}|2[0-4]\d|25[0-5])\.){3}(1?\d{1,2}|2[0-4]\d|25[0-5])$/

[badgoat]

Excellent, that's even shorter! Much appreciated 🙂