如何在php中为变量上传设置我的目标文件夹?

I am new to php, hence cannot figure out my problem. I have an HTML form that is connected to the mentioned php file. This form works fine. The problem is with the php file. The HTML form is:

    <!DOCTYPE html>
    <html>
    <body>

    <form action="upload.php" method="post" enctype="multipart/form-data">
    Select image to upload:
    <input type="file" name="fileToUpload" id="fileToUpload">
    <input type="submit" value="Upload Image" name="submit">
    </form>

    </body>
    </html>

And my php file called upload.php is:

    <?php
    $uid = $_POST['uid'];
    $target_dir = "FILES OF:$uid";
    $target_file = $target_dir . basename($_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["submit"])) {
    $check = getimagesize($_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;
    }
    }
    ?>

Here, as you can see in the first lines of the php code, the target directory is set. But I want it to be with a variable called

    $uid

which is linked to the uid field in my database meaning username. What I mean to say is that I want it to upload files in the folder called "FILES OF:$uid". I have these folders already created but want a way in which files will go directly to that folder. Does anyone know a way to do this?

hi i have link where you can check your code is correct or not if you don't want to check link then check following code.

image upload to specific folder

following code is copy from given link

 <?php
    $target_dir = "uploads/";
    $target_file = $target_dir . basename($_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["submit"])) {
        $check = getimagesize($_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)) {
        echo "Sorry, file already exists.";
        $uploadOk = 0;
    }
    // Check file size
    if ($_FILES["fileToUpload"]["size"] > 500000) {
        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;
    }
    // Check if $uploadOk is set to 0 by an error
    if ($uploadOk == 0) {
        echo "Sorry, your file was not uploaded.";
    // if everything is ok, try to upload file
    } else {
        if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
            echo "The file ". basename( $_FILES["fileToUpload"]["name"]). " has been uploaded.";
        } else {
            echo "Sorry, there was an error uploading your file.";
        }
    }
    ?>