The = operator is special in that you can combine it with other operators. For example, to turn > (greater than) into greater than or equals, add the equals sign to the end - >=. You can add an equals sign to each of the first six operators in the list, forming +=, -=, *=, /=, and .=, and these become unary operators, like this:
$somevar=5; $somevar+=5;// $somevar is now 10 $somevar*=2;// $somevar is now 20 $somevar.=" elephants";// $somevar is now "20 elephants" ?>
The unary versions of these operators are really just shorthand, but they are a little easier to read also.