Are you have problems with automated SPAM bots submitting to your PHP form? This can easily be fixed by adding a CAPTCHA to your form. CAPTCHA stands for: Completely Automated Public Turing test to tell Computers and Humans Apart. The main purpose of a CAPTCHA is to distinguish human from a computer. A code or image is presented in a way that only a human would be able to understand, so say good bye to automated SPAM!
There are a large number of CAPTCHAs available. The three that I use are
reCaptcha is made by Google and it is one of the most popular solutions available. reCaptcha is easy to setup and has multiple libraries for almost any programming language available. Google also uses reCaptcha to digitize old books and newspapers.
Securimage is a PHP based captcha system that has much more customization options then reCaptcha. Almost every aspect can be configured to make it fit in with your forms. Securimage generates an image with text that is hard for computers to decipher. The complexity of the captcha can be configured to meet you websites’ needs.
visualCaptcha is a unique captcha system that uses images instead of text to test the user. It will show a series of images and tell you to click a certain image. Has libraries for PHP, Ruby, and NodeJS. It is one of the most friendly and easy to use captchas.