Code explanation of string format calculation formula using eval in php

Sometimes we have a royalty 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 the one we wrote: $ a2 + 3*5; in this way, the result can be calculated simply, and it is a string. therefore, we must convert the string into the result that we can process. sometimes we have a Commission formula for each product, and the formula for this computation is stored in the table in the string format, when we use this formula, it is not as simple as we write: $ a = 2 + 3*5; it can calculate the result, and it is a string. therefore, we must convert the string into the result that we can process.

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.

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The above is a detailed explanation of the code for implementing the string format calculation formula through eval in php. For more information, see other related articles in the first PHP community!