根据生日计算年龄

function age($date){  
    $year_diff = '';  
    $time = strtotime($date);  
    if(FALSE === $time){  
        return '';  
    }  
 
    $date = date('Y-m-d', $time);  
    list($year,$month,$day) = explode("-",$date);  
    $year_diff = date("Y") – $year;  
    $month_diff = date("m") – $month;  
    $day_diff = date("d") – $day;  
    if ($day_diff < 0 || $month_diff < 0) $year_diff–;  
 
    return $year_diff;  
}