Checking if a string is a double or not

You can try this:

function isfloat($num) {
    return is_float($num) || is_numeric($num) && ((float) $num != (int) $num);
}

var_dump(isfloat(10));     // bool(false)
var_dump(isfloat(10.5));   // bool(true)
var_dump(isfloat("10"));   // bool(false)
var_dump(isfloat("10.5")); // bool(true)

// Try to convert the string to a float
$floatVal = floatval($num);
// If the parsing succeeded and the value is not equivalent to an int
if($floatVal && intval($floatVal) != $floatVal)
{
    // $num is a float
}

This will omit integer values represented as strings:

if(is_numeric($num) && strpos($num, ".") !== false)
{
    $this->print_half_star();
}