Implementation of converting time difference into string in php

<?php 
class timeAgo 
{ 
static $timeagoObject; 
private $rustle; 
private $unit; 
private function __construct() 
{ 
} 
private function __clone(){ } 
public static function getObject() 
{ 
if(! (self::$timeagoObject instanceof self) ) 
self::$timeagoObject = new timeAgo(); 
return self::$timeagoObject; 
} 
private function count_int($unix_C) // main function 
{ 
if(! (isset($unix_C) || is_numeric($unix_C)) ) 
return &#39;don\&#39;t find parameter&#39;; 
$d = time()-$unix_C ; // $d - unix time difference value 
$d_int =(int)floor($d/60) ; // minimum unit -- minutes unix/60 
$this->unit = 0 ; // is minutes,hour or day? 
if($d_int < 60){ // minutes in one hour 3600 
$this->rustle = $d_int; 
$this->unit = 1; 
} 
else if($d_int < 720){ //hour in one day 3600*12 
$this->rustle = floor($d_int/60); 
$this->unit = 2 ; 
} 
else if($d_int < 7200){ //day in ten days 3600*12*10 
$this->rustle = floor($d_int/720); 
$this->unit = 3 ; 
} 
else{ 
$this->rustle = $d ; 
$this->unit = 4 ; 
} 
} 
public function piece_str($C) 
{ 
$this->count_int($C); 
$u = &#39;&#39;; 
switch( $this->unit ) 
{ 
case 1: 
$u = &#39;minute&#39;; 
break; 
case 2: 
$u = &#39;hour&#39;; 
break; 
case 3: 
$u = &#39;day&#39;; 
break; 
case 4: 
$u = &#39;&#39;; 
break; 
case 0: 
return &#39;sorry , get time is fail&#39;; 
} 
if($this->unit < 4) 
{ 
if($this->rustle > 1) 
return (string)$this->rustle.$u.&#39;s ago&#39;; 
else if($this->rustle == 1) 
return (string)$this->rustle.$u.&#39;ago&#39;; 
else 
return &#39;Just now&#39;; 
} 
} 
/* example: $ago = timeAgo::getObject(); 
* echo $ago->piece_str($unix); 
* // 2 days ago 
*/ 
} 
?>