here's my rot function, it works anyway
<?php
/**
 * preforms the rotation algorithm on the passed in string
 */
function _rot( $str , $dist=13 ){
    if( !is_numeric($dist) || $dist < 0){
        $dist = 13;
    }

    $u_lower =  65; $u_upper =  90;
    $l_lower =  97; $l_upper = 122;
    
    $char_count = ($u_upper - $u_lower) +1;

    while( $dist > $char_count ){
        $dist -= $char_count;
    }

    $newstr = '';
    
    for( $i=0; $i<strlen($str); ++$i){
        $c = ord($str[$i]);

        /*
         * Check if the character is within the bounds of our function (a-zA-z)
         * if not it gets tacked on to the string as is and we move on to the 
         * next one.
         */
        if( $c<$u_lower || $c>$l_upper || ( $c>$u_upper && $c <$l_lower ) ){
            $newstr .= chr($c);
            continue;
        }

        $lower = ( $c<=$u_upper?$u_lower:$l_lower);
        $upper = ( $c<=$u_upper?$u_upper:$l_upper);

        $c += $dist;

        if( $c > $upper){
            $c = (($c - $upper) + ($lower-1));
        }

        $newstr .= chr($c);
    }
    
    return $newstr;
}
?>