The Four-Function Calculator: Our First Simple Application

We can combine this understanding of statefulness and events to make our first simple Qforms application.

This calculator is just a collection of two QTextBox objects (one for each operand), a QListBox object containing the four arithmetic functions, a QButton object to execute the operation, and a QLabel to view the result. Note that there is no validation, checking, etc. currently in the Qform. Any string data will be parsed by PHP to see if there is any numeric data, and if not, it will be parsed as 0. Dividing by zero will throw a PHP error.