PHP file upload fail with error code 0

I'm trying to upload files to a remote server. The target folder IEEE owner/group set as: se07 se07. What I have to do is to upload files to IEEE directory.

$target_dir = "/var/www/se07/uploads/IEEE/";

Here's what I did :

Adding a prefix to file names

$Profile_fileName = $_FILES['Profile_file']['name'];    
$Profile_target_file = $target_dir. $passportNumber ."/". basename('Profile_'.$Profile_fileName);

$Passport_fileName = $_FILES['Passport_file']['name'];
$Passport_target_file = $target_dir. $passportNumber ."/". basename('Passport_'.$Passport_fileName);

$ID_card_fileName = $_FILES['ID_card_file']['name'];
$ID_card_target_file = $target_dir. $passportNumber ."/". basename('ID_card_'.$ID_card_fileName);  

Create directory if it does not exist

if(!is_dir($target_dir. $passportNumber ."/")) {
    mkdir($target_dir. $passportNumber ."/");
}

Move the uploaded file

if (move_uploaded_file($_FILES["Profile_file"]["tmp_name"], $Profile_target_file)) {
    chmod($Profile_target_file, 0755);
    echo "Stored in: " . $Profile_target_file;
} else {
    echo "Not uploaded because of error #".$_FILES["Profile_file"]["error"];
    $error = true;
}        
if (move_uploaded_file($_FILES["Passport_file"]["tmp_name"], $Passport_target_file)) {
    chmod($Passport_target_file, 0755);
    echo "Stored in: " . $Passport_target_file;
} else {
    echo "Not uploaded because of error #".$_FILES["Passport_file"]["error"];
    $error = true;
}  
if (move_uploaded_file($_FILES["ID_card_file"]["tmp_name"], $ID_card_target_file)) {
    chmod($ID_card_target_file, 0755);
    echo "Stored in: " . $ID_card_target_file;
} else {
    echo "Not uploaded because of error #".$_FILES["ID_card_file"]["error"];
    $error = true;
} 

However, I got the following message:

Not uploaded because of error #0

And error code 0, according to the manual stands for "UPLOAD_ERR_OK - There is no error, the file uploaded with success." but I can't figure out why it wasn't uploaded.

Where is the mistake? Thank you!