PHP code in views calculations

I am currently working on some views that relate to school years. These are *really* hard to show with PHP's built in functions. I'd love it if I had the ability to write my own function to provide a date boundary for a view. For example, a semester view:

if(now() > sept && now() < dec) {
    return "december 31";
} elsif(now() > jan && now() < jun) {
    return "june 30";
} else {
    return "august 31";
}