使用Zend Server的apc_fetch PHP 5.3

Question

I encountered a problem when I wanted to show a process bar in a file upload.

My php version is 5.3.14. My zend server version is 5.6. I turned off the Zend Data Cache & Zend Optimizer+.

Here is my upload code.

<?php
$uiq = uniqid();
$image_folder = "uploads/";
$uploaded = false;

if(isset($_POST['upload_image'])){ 
    if($_FILES['userImage']['error'] == 0 ){
        $up = move_uploaded_file($_FILES['userImage']['tmp_name'],     $image_folder.$_FILES['userImage']['name']);
        if($up){
           $uploaded = true;   
        }
    }
 }
?>

Following is my process code called by ajax.

if(isset($_GET['progress_key']) and !empty($_GET['progress_key'])){ 
    $status = apc_fetch('upload_'.$_GET['progress_key']);
    if($status){
        echo $status['current']/$status['total']*100;
    }else{
        echo 0;
    }  
exit;
}

The apc_fetch function always return false. Does anyone know the reason?