php文件无法上传，错误代码为0

I am trying to upload files using php to directory that is not in the same directory that the upload script is, here is the structure of dir's:

var>www>html>
            foo>index.php //this ones where upload is done
            bar>          //this is where I want to upload it

the index.php file's form element:

<form enctype="multipart/form-data" method="POST" action="index.php">
            <fieldset style='width:33%;'>
                <legend>UPLOAD PROJECT FILES</legend>
                <select name="dirList" id="dirList" onChange="getSubDir(this.value)" required>
                    <option value="">SELECT PROJECT</option>
                    <?php
                        $path = "../";
                        $scan = scandir($path);
                        foreach($scan as $result){
                            if($result === '.' or $result === '..') continue;
                            if(is_dir($path . '/' . $result)){
                                echo "<option value='../$result'>$result</option>";
                            }
                        }
                    ?>
                </select>
                <select name="subDirList" id="subDirList">
                    <option value="">SELECT PATH</option>
                </select>
                <input type="file" name="filePath"/>
                <input type="submit" name = "upload" value="UPLOAD"/>
            </fieldset>
        </form>

so the idea here is to get the list of folders from first combobox which will get me the list of subdirectories in the second combobox.

and then the php function at the head of index.php for uploading the file:

if(isset($_POST['upload'])){
            $upload_path = $_POST['subDirList'];
            if($upload_path == ''){
                $upload_path = $_POST['dirList'];
            }
            $upload_path = getcwd().'/'.$upload_path;
            $upload_path = $upload_path.'/'.basename($_FILES['filePath']['name']);              
            if(move_uploaded_file($_FILES["filePath"]["tmp_name"], $upload_path)){
                echo "success";
            } else {
                echo print_r($_FILES);
                echo 'fail';
            }

        }

the error log:

[Wed Sep 23 14:10:46.841250 2015] [:error] [pid 4028] [client 78.167.168.253:52438] PHP Warning:  move_uploaded_file(): Unable to move '/tmp/phpEB1a3s' to '/var/www/html/eShop/Capture.PNG' in /var/www/html/ftp/index.php on line 16, referer: http://xxx.xx.xx.xx/ftp/index.php

Check if you have writte permissions.

Then, by documentation also check if the file name is valid, and remeber the warning:

Warning If the destination file already exists, it will be overwritten.

As a suggestion, always check that :

isset($_FILES["FileInput"]) && $_FILES["FileInput"]["error"]== UPLOAD_ERR_OK)

is true before continuing.