Is this PHP Email Form Secure from injections or other abuses?
I use a blank input field in the form and hide it with css.  If the field exists upon form submit, I know it's spam and just ignore it.

&lt;form method="post"&gt;
&lt;input type="text" name="email" /&gt;
&lt;input type="text" name="email2" style="display:none;" /&gt;
&lt;input type="submit" /&gt;
&lt;/form&gt;

&lt;?php if (!$_POST['email2']) { // not spam } ?&gt;


Of course this only works with bots and spammers who scrape sites to get all the input fields, but since I've implemented it, it's worked great.