If logic (predicate expression) in a variable

I'm passing the comparison operator as a variable to the PHP Cli:

./test.php -k "command" -c ">0"

The command in -k products a result and I've stored it in $result

The problem I'm getting is I want to pass the logic and comparison operator as variables, is this possible?

$result = 2;
$logic = ' >0';

if ( $result $logic ) echo "true"; 

But I get:

PHP Parse error: syntax error, unexpected '$logic' (T_VARIABLE)

Any ideas?