Help work out age in PHP

Ok this is simple but I don’t know jack about mysql or php.

In flash I have a “dob” list box.

This pulls the dob from mysql in the for of “1989”

 $dob = mysql_result($fewComments, $i, 'dob');

This is where I am sending that information to flash, but I dont want to send 1989, I want to send 15.

print "<br>&writeage=";
if($numallComments == 0) { print "	 No entries yet.."; } 
else { $i = 0;
$dob = mysql_result($fewComments, $i, 'dob');
print'<b>Age: </b>'. $dob .'';}

I am assuming it is CURRENTDATE() - 1989 but I don’t know how to format CURRENTDATE so I can minus 1989

Any help or hints much appreciated…