I want to have a class property that allow for an expression to take place on the right side of the equals sign. All versions of PHP choke on the following code, but it is written in this way to allow for easier extendibility in the future.

/* Example SDK Class */
class SDK
{
    /* Runtime Option Flags */
    // Strings
    #  0: Makes no change to the strings.
    var $STRING_NONE        = (1 << 0);
    #  1: Removes color codes from the string.
    var $STRING_STRIP_COLOR = (1 << 1);
    #  2: Removes language codes from the string.
    var $STRING_STRIP_LANG  = (1 << 2);
    #  3: Removes all formatting from the string.
    var $STRING_STRIP       = SELF::STRING_STRIP_COLOR & SELF::STRING_STRIP_LANG;
    #  4: Converts color codes to HTML & UTF-8.
    var $STRING_HTML        = (1 << 3);
    #  8: Converts color codes to ECMA-48 escape color codes & UTF-8.
    var $STRING_CONSOLE     = (1 << 4);
    # 16: Changes player names only.
    var $STRING_NAMES       = (1 << 5);
    # 32: Changes host names only.
    var $STRING_HOSTS       = (1 << 6);
    function SDK($fString = SELF::STRING_HTML & SELF::STRING_NAMES & SELF_HOST)
    {
        // constructor code.
    }
}

$SDK &= new SDK(SDK::STRING_NONE);

(1 << 0) seems like very basic syntax to me, and is not fathomable why PHP would not allow for such a thing. Can anyone think of a work around that would maintain readability and future expandability of the following code?