PHP implementation of a simple web version of the Calculator function method

This article mainly introduces the PHP programming to achieve a simple web version of the calculator function, involving PHP simple form operation and numerical computing related implementation skills, the need for friends can refer to the following

How to use PHP code to implement a web version of the calculator simple function? The following is the PHP basic knowledge to do the web version of the calculator, the function only "add and subtract residual", some other computing functions can be expanded.

The specific PHP code that implements the simple calculator is as follows (this is all the code for PHP file jsq.php):