php将日期格式转换成xx天前的格式

// convert a date into a string that tells how long ago
// that date was.... eg: 2 days ago, 3 minutes ago.
function ago($d) {
 $c = getdate();
 $p = array(year, mon, mday, hours, minutes, seconds);
 $display = array(year, month, day, hour, minute, second);
 $factor = array(0, 12, 30, 24, 60, 60);
 $d = datetoarr($d);
 for ($w = 0; $w < 6; $w++) {
 if ($w > 0) {
  $c[$p[$w]] += $c[$p[$w-1]] * $factor[$w];
  $d[$p[$w]] += $d[$p[$w-1]] * $factor[$w];
 }
 if ($c[$p[$w]] - $d[$p[$w]] > 1) { 
  return ($c[$p[$w]] - $d[$p[$w]]). .$display[$w].s ago;
 }
 }
 return ;
}
// you can replace this if need be. 
// This converts my dates returned from a mysql date string 
// into an array object similar to that returned by getdate().
function datetoarr($d) {
 preg_match("/([0-9]{4})(\\-)([0-9]{2})(\\-)([0-9]{2})([0-9]{2})(\\:)([0-9]{2})(\\:)([0-9]{2})/",$d,$matches);
 return array( 
 seconds => $matches[10], 
 minutes => $matches[8], 
 hours => $matches[6], 
 mday => $matches[5], 
 mon => $matches[3], 
 year => $matches[1], 
 );
}