how execute different code depending on the number and type of arguments passed to a method?

PHP doesn't support method polymorphism as a built-in feature. However, you can emulate it using various type-checking functions. The following combine( ) function uses is_numeric(), is_string(), is_array(), and is_bool():

// combine() adds numbers, concatenates strings, merges arrays,
// and ANDs bitwise and boolean arguments
function combine($a, $b) {
    if (is_numeric($a) && is_numeric($b)) {
        return $a + $b;
    }

    if (is_string($a)  && is_string($b))  {
        return "$a$b";
    }

    if (is_array($a)   && is_array($b))   {
        return array_merge($a, $b);
    }

    if (is_bool($a)    && is_bool($b))    {
        return $a & $b;
    }

    return false;
}