Using eval in php to calculate the string format, eval string

Using eval in php to calculate the string format, eval string

Sometimes we have a Commission formula for each product, and the formula used for this calculation exists in the table in the string format. When we use this formula, it is not like what we wrote: $ a = 2 + 3*5; this is a string that can calculate the result. therefore, we must convert the string into the result that we can process.
The eval () function in php can process php code, so it can be used to solve the problem: the formula stored in string format

For example:

$ Str = '2*(3 + 12) '; $ result = eval ("return $ str;"); echo $ result;

Output: 30

Is the expression value

The return $ str; In eval () is the php code.

Of course, you can also include the variable value:

$ A = 3; $ B = 12; $ str = '2 * ($ a + $ B) '; $ result = eval ("return $ str ;"); echo $ result;

Output: 30

In this way, php implements the calculator code, mainly using the eval function of php.