string array_sort_by_day(array)

This handy PHP function will sort an array by the order of the days in a week.  Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday.
Simply sorting the array alphabetically would result in the days being out of sequential order.

function array_sort_by_day($values){
// Function written by Marcus L. Griswold (vujsa)
// Can be found at http://www.handyphp.com
// Do not remove this header!
    $search_strings = array("Sunday","Sun","Su","Monday","Mon","Mo","Tuesday","Tues","Tue","Tu","Wednesday","Wed","We","Thursday","Thurs","Thur","Thu","Th","Friday","Fri","Fr","Saturday","Sat","Sa");
    $replace_string = array('0','0','0','1','1','1','2','2','2','2','3','3','3','4','4','4','4','4','5','5','5','6','6','6');
    $sort_key = array_map('ucfirst', $values);
    $sort_key = str_replace($search_strings, $replace_string, $sort_key);
    array_multisort($sort_key, SORT_ASC, SORT_STRING, $values);
    return $values;
}

$days = array("Monday1123.html","Wednesday122.html","Sun332.html","Friday542.html","Tues14556.html","Sunday7819.html","Mon3221.html","Saturday8952.html","Thursday9603.html");
echo "<pre>\n";
var_dump(array_sort_by_day($days));
echo "</pre>\n";

array(9) {
 [0]=>
 string(11) "Sun332.html"
 [1]=>
 string(15) "Sunday7819.html"
 [2]=>
 string(15) "Monday1123.html"
 [3]=>
 string(12) "Mon3221.html"
 [4]=>
 string(14) "Tues14556.html"
 [5]=>
 string(17) "Wednesday122.html"
 [6]=>
 string(17) "Thursday9603.html"
 [7]=>
 string(14) "Friday542.html"
 [8]=>
 string(17) "Saturday8952.html"
}

This would work for all English day names and their abbreviations.  If used for file sorting as suggested here, it would be advisable to validate the filenames prior to uploading them to ensure that the day names will be identified properly.
Function inspired by a discussion at Trap17.com.  Thanks to BuffaloHelp for the inspiration!