Code Golf: Print the entire "12 Days of Christmas" song in the fewest lines of code

PHP

$g = array("a partridge in a pear tree.\n",
    "two turtle doves, and",
"three french hens,",
"four calling birds,",
"five gold rings,",
"six geese a-laying,",
"seven swans a-swimming,",
"eight maids a-milking,",
"nine ladies dancing,",
"ten lords a-leaping,",
"eleven pipers piping,",
"twelve drummers drumming,"
);
$d = array("first", "second", "third", "fourth", "fifth", "sixth",
 "seventh", "eighth", "nineth", "tenth", "eleventh", "twelfth");
foreach($d as $i=>$v){
    echo "On the $v day of Christmas my true love gave to me";
    for($j=$i;$j>=0;$j--) echo " ",$g[$j];
}

Another C#

var l="a partridge in a pear tree.|two turtle doves, and|three french hens,|four calling birds,|five gold rings,|six geese a-laying,|seven swans a-swimming,|eight maids a-milking,|nine ladies dancing,|ten lords a-leaping,|eleven pipers piping,|twelve drummers drumming,".Split('|');

for (int i = 1; i < 13; i++)
    Console.Write(
        "On the {0}{2} day of christmas\rmy true love gave to me \r{1}\r\r", 
            i, 
            string.Join("\r", l.Take(i).Reverse().ToArray()), 
            (i==1?"st":i==2?"nd":i==3?"rd":"th"));

Borrowed heavily from previous answers (hey, code reuse) while adding extra savings.

481 characters once you take out unnecessary whitespace:

var l="a partridge in a pear tree.|two turtle doves, and|three french hens,|four calling birds,|five gold rings,|six geese a-laying,|seven swans a-swimming,|eight maids a-milking,|nine ladies dancing,|ten lords a-leaping,|eleven pipers piping,|twelve drummers drumming,".Split('|');for(int i=1;i<13;i++)Console.Write("On the {0}{2} day of christmas, my true love gave to me \r{1}\r\r",i,String.Join("\r",l.Take(i).Reverse().ToArray()),(i==1?"st":i==2?"nd":i==3?"rd":"th")); 

423 bytes with Lingua::EN::Number:

use Lingua::EN::Numbers qw/num2en num2en_ordinal/;
@l=map{($i++?num2en($i):'a')." $_"}split/\n/,<<"";
partridge in a pear tree
turtle doves, and
french hens
calling birds
gold rings
geese a-laying
swans a-swimming
maids a-milking
ladies dancing
lords a-leaping
pipers piping
drummers drumming

print"On the ".num2en_ordinal($_+1)
." day of Christmas, my true love gave to me ",
join(', ',reverse@l[0..$_]),"\n\n"for(0..11);

Or 480 bytes in perl without using Lingua::EN::Numbers:

@n=qw/first second third forth fifth sixth seventh eigth nineth tenth eleventh twelfth/;
@l=<DATA>;chomp@l;
print"On the $n[$_] day of Christmas, my true love gave to me ",
join(', ',reverse@l[0..$_]),"\n\n"for(0..11);
__DATA__
a partridge in a pear tree
two turtle doves, and 
three french hens
four calling birds 
five gold rings 
six geese a-laying
seven swans a-swimming
eight maids a-milking
nine ladies dancing
ten lords a-leaping
eleven pipers piping
twelve drummers drumming

It should be able to be reduced further since the numbers are very repetitive.