How safe is PHP?

PHP is like the electricity or kitchen knives in your home: handled properly, it is very safe, handled irresponsibly, it can do a lot of damage. PHP is unsafe; nor does everyone need to become a security expert to use PHP. What is important is to understand the basic principle of PHP safety: always check user input before processing it. Most security risks can be eliminated with very little effort. The other important thing is to know enough about scripts that you are using, so that if a problem arises, you can implement any remedies suggested to you by the author of the script or another expert.