How can I avoid vote spam on my PHP site
<p>I am doing a voting system on my website. </p>

<p>Visitors do not need to login to vote the product they like. But how can I prevent them from clicking the like or dislike button many times for one product ?</p>

<p>I intend to detect the IP address of the visitor to avoid vote spam. Is that a good way?</p>

<p>Thanks for any suggestions!</p>
