Randomly Generated Numeric Symbol

programming
1

I used the following code to generate +, - and *

function symbol() {
    $values = "+-*";
    $string = $values{rand(0, 2)};
    return($string);
}

And I have two numbers 3 and 4

I want to used the randomly generated symbol to either add, minus or time 3 and 4. How do I do that using PHP? Thanks in advance