PHP 在两个值之间使用连接逻辑运算符 - 数学

Question

Hi I'm retrieving some values form my database using Laravel in order to calculate something.

This is a really simple version of what I have (i have a config which has multiple of these values and I pass the model names and values and Im able to do this on the fly):

 $substitute['operator'] = '/';
 $substitute['value'] = '5';

 $select = User::->where('id','1')
                  ->pluck('holidaysperyear');


 $replace = $select.$substitute['operator'].$substitute['value'];

If I concatenate the logical operator the values are all printed out eg 21/5

however if I do this:

 $replace = $select/$substitute['value'];

The division is done successfully but the problem I have is that I have config which could want the operator to be multiplied or addition so I would need the flexibility to pass in the operator, any ideas why it doesn't work like that? help is appreciated!

Answer 1

In order to do what you're asking, you would have to eval() the string. That isn't good practice however, so here is another solution.

You could use a switch statement with each valid operator, and just perform the proper operation in the case statement. Like this:

switch ($substitute['operator']) {
    case '*':
        $replace = $select * $substitute['value'];
        break;
    case '/':
        $replace = $select / $substitute['value'];
        break;
    case '+':
        $replace = $select + $substitute['value'];
        break;
    case '-':
        $replace = $select - $substitute['value'];
        break;
    case '%':
        $replace = $select % $substitute['value'];
        break;
    case '**':
        $replace = $select ** $substitute['value']; // or pow() if you use < PHP 5.6
        break;
    // more cases...
}