Changes

Through the use of parentheses around the addition expression we have changed the ''operator precedence'' for that expression.

All of the operators we have looked at so far are similar to those available in other programming and scripting languages. With the execution operator, however, we begin to experience the power of PHP as server side scritping environment. The execution operator allows you to execute a command on the operating system that hosts your web servber and PHP module and then capture the output.