The masses of coding involved did begin to take its toll, but here it is finally in its entirety:
<?="../BPStrips/" . (date("W") == date("W", mktime(0, 0, 0, 12, 25, 2008)) ? "Xmas" : "Week" . (date("W") > 51 ? 51 : date("W"))) . "/strip3.jpg";?>
Peepmaster will explain it to you all.