php根据生日计算年龄的方法

<?php 
function birthday($birthday){ 
  $age = strtotime($birthday); 
  if($age === false){ 
    return false; 
  } 
  list($y1,$m1,$d1) = explode("-",date("Y-m-d",$age)); 
  $now = strtotime("now"); 
  list($y2,$m2,$d2) = explode("-",date("Y-m-d",$now)); 
  $age = $y2 - $y1; 
  if((int)($m2.$d2) < (int)($m1.$d1)) 
    $age -= 1; 
  return $age; 
} 
echo birthday(‘1986-07-22‘); 
?>