[SOLVED] randomly add, subract or multiply

[Dragen]

okay, this is probably a stupid question, but I can't figure out an answer..

I'm trying to randomly add, subtract or multpily from a number. I create the number and also the second number which will be used for the equation.

I've also got the mathematic operators (I hope that's the right term..) stored in an array:

$matho = array('+', '-', '*');

 

How can I then get php to parse it all as a mathematics equation?

I mean this obviously doesn't work:

echo $number1 . $matho[rand(0, 1)] . $number2;

 

thanks

[DylanBlitz]

I'd do it like this

 

$matho = array('+', '-', '*');
$math_var = $matho[rand(0, 2)];

switch ($math_var)
{
case '+':
	echo $number1 + $number2;
	break;
case '-':
	echo $number1 - $number2;
	break;
case '*':
	echo $number1 * $number2;
	break;
}

[Darklink]

You can't bring up an equation symbol from a variable without using eval.

 

The following code should work (or something similar using eval). I don't use eval as much anymore but I know it's something like this.

 

$matho = array('+', '-', '*');
eval("echo $number1 " . $matho[rand(0,2)] . " $number2;");

[simshaun]

I would shy away from using eval if you are letting users enter their own input.  It's too much of a security risk.

 

DylanBlit's method is the way I would do it.

 

The only exception is I would change $math_var to this for sake of making it just a little more dynamic and easier to read:

srand((float)microtime() * 1000000); // (PHP4 Only) make it more random.
shuffle($matho);
$math_var = $matho[0];

[Dragen]

thanks for the advice guys. eval is something I hadn't looked into before.

I'm really not wanting to have to write out a whole switch statement just for a simple maths equation. It means that each time I want to change an operator I have to change the whole thing.

I've gone with darklink's suggestion of eval as I don't need to worry about user input or anything and it's quicker to make changes.

Here's my eval solution:

$n = rand(1, 75);
$n2 = rand(1,12);
eval("\$this->check = $n" . $matho[$opt] . "$n2;");