PHP Detect how many URLS in the string

Question

I'm implementing a contact form for a website, and I'd like to avoid using a captcha because I believe it has a negative effect on user experience.

Instead, I've decided to trial detecting the number of URLs that have been submitted with the message.

I am retrieving the message as a string from the $_POST submission. I know inbuilt PHP functions such as stristr() can give me confirmation that a substring exists within the message but what I'd like is the count.

Also, in terms of spam detection, would a match on something like "</a>" be appropriate?

Cheers.

Answer 1

substr_count($text, "http") http://www.php.net/manual/en/function.substr-count.php

Note that isn't sufficient, but neither is allowing users to enter unfiltered data into your form fields that gets rendered as html.

I shouldn't be able to put javascript in there either due to Cross Site Scripting http://www.owasp.org/index.php/Top%5F10%5F2007-Cross%5FSite%5FScripting

I'd recommend using http://htmlpurifier.org/ to remove any malicious code.

Finally for spam filtering I'd recommend http://akismet.com/

Good luck.

Answer 2

if this is a contact form, there is no need to accept html. just encode the whole content and limit the number of posts from the same ip or limit the time between messages.

yes you could restrict the number of urls, but i don't think this is effective