上传文件到目标文件夹有问题

我是PHP新手，还在学习…今天我不明白为什么文件是从目标目录$target_dir上传的。我改变了$target_dir很多次，但我总是得到相同的结果。代码看起来很好…

任何想法?

谢谢. .

 function avatarUpload(){
    $target_dir = "../uploads/avatars/";
    $target_file = basename($_FILES["fileToUpload"]["name"]);
    $uploadOk = 1;
    $imageFileType = pathinfo($target_file,PATHINFO_EXTENSION);
    // Check if image file is a actual image or fake image
    if(isset($_POST["avatar"])) 
    {
        $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
        if($check !== false) 
        {
            //echo "File is an image - " . $check["mime"] . ".";
            $uploadOk = 1;
        } else  {
           // echo "File is not an image.";
            $uploadOk = 0;
        }
    }
    // Check if file already exists
    if (file_exists($target_file)) 
    {
        do
        {
            $rand = rand(100,10000);
            $target_file = $rand .= $target_file;
        } 
        while( file_exists($target_file) );
    }
    // Check file size
    if ($_FILES["fileToUpload"]["size"] > 5000000000) 
    {
        //echo "Sorry, your file is too large.";
        $uploadOk = 0;
    }
    // Allow certain file formats
    if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
    && $imageFileType != "gif" ) {
    echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
    $uploadOk = 0;
    } else {
        if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)== true) 
        {
           // echo "The file ". basename( $_FILES["fileToUpload"]["name"]). " has been uploaded.";
           return $target_file;
        } else 
        {
           // echo "Sorry, there was an error uploading your file.";
           return $target_file;
        }
    }

    return $target_file;
    }