This allows you to check for the existence of a variable (or check that the variable has a valid value) and assign a value accordingly. This is very useful when you are dealing with $_GET, $_POST, $_SESSION etc. variables, because you don't know whether the incoming variable will exist, and if it doesn't you might want to assign a default value.

An example is included and explained - evaluating an index in the _GET superglobal to see if it exists. It returns either the value itself or a false.

An operator is a special character or combination of characters that operates on variables. There are 3 types of operators in PHP: unary, binary and ternary. They can be used to manipulate a variable with up to 3 arguments at a time. This article wasn't written to discuss the meaning and usage of each operator in PHP, but rather to explain the differences between these types of operators and to give examples about how each functions.

They look at the different types of operators (and include examples for each) - unary (like ! or ++), binary (things like + / == and &&) and a special case - ternary. This uses two characters in conjunction (the question mark and colon) to replace a simple sort of If statement.