I have 3 variables :
$a = 5;
$b = 3
$o = "*";
The $o variable contains a string value. This value can also be "/", "+", "-".
So when I concatenate $a.$o.$b :
$result = $a.$o.$b;
echo $result;
The result is 5*3 (a string) instead of 15.
So how to convert operator string into real operator ?
You can't, you'd need to make a function or a switch statement to check each of the operators.
Read this question and its answers so you'll understand how to do it.
Simple, short and save solution:
$a = 5;
$b = 3
$o = "*";
$simplecalc = function($a,$b,$op) {
switch($op):
case "*":
return $a*$b;
case "+":
return $a+$b;
case "-":
return $a-$b;
case "/";
return $a/$b;
default:
return false;
endswitch;
};
$result = $simplecalc($a,$b,$o);
Actually you can do it, by using eval. But it hurts to recommend using eval, so I just give you a link to another question with a good answer: calculate math expression from a string using eval
You can use eval. For example:
eval('echo 5*3;')
will echo the number 15.
I believe this is what you are looking for.
$a = 5;
$b = 3;
$o = "*";
$result = eval( "echo $a$o$b;" );
echo $result;
Please note that using eval() is very dangerous, because it allows execution of arbitrary PHP code.
switch($o) {case '+': $result = $a + $b; break; case '-': $result = $a - $b; break; case '*': $result = $a * $b; break; case '/': $result = $a / $b; break; }