Why would PHP not always upload a file - php

Question

On a PHP page, I call an upload function that contains the standard PHP upload procedure. After I call the function, I do a redirect (tried with either window. location or header ()).
The strange thing is that everything works fine a couple of times, then it would not upload anymore (uploadOK won't be 0 either). It would just not move the file onto the server.
Then, I would take out the redirect and the upload would start working again. I put the redirect back in, the upload will still work a couple of times then stop again... Do you have any idea why?
Another strange thing is that, even when it doesn't work, the upload function still returns the correct path+filename, but it would not echo "File ... was uploaded".
I suspect that the problem might be in the move_uploaded_file() function... but it would not return 0, because "Error..." would not be echoed.
Without calling the redirect after the upload, it uploads fine every time.
PHP page:
$_SESSION["temp_file_name"]="../".UploadFisier($_FILES["fileToUpload"], $_SESSION["ID_CLASA"]."_".$id_item."_temp_".UserIdLogat($dbocr)."_", "../teme/", "");
header("Location: trimite_tema_script.php");
The Upload function:
function UploadFisier($file, $sufix, $target_dir, $maxsize)
{
if ($maxsize=="") { $maxsize=3000000; }
if ($target_dir=="") { $target_dir="../upload/"; }
$target_empty_file=$target_dir.$sufix;
$target_file = $target_empty_file.basename($file["name"]);
$uploadOk = 1;
if ($target_file != $target_empty_file)
{
if ($file["size"] > $maxsize)
{
echo "file too large";
$uploadOk = 0;
}
}
else
{
echo "no file selectec.";
$uploadOk = 0;
}
if ($uploadOk == 1)
{
//we overwrite
if (file_exists($target_file))
{
unlink($target_file);
}
if (move_uploaded_file($file["tmp_name"], $target_file))
{
echo "File ". basename( $file["name"]). " was uploaded.";
//we output the path and filename without the "../" at the beginning
$linksave=substr($target_file, 3);
}
else
{
echo "Error....";
}
}
echo "uploadOk ".$uploadOk;
return $linksave;
}

Answer 1

Check the file_uploads value in PHP.ini and confirm that is something like this
file_uploads = On

Answer 2

Wrap a try/catch in your code. maybe you will find out more about the error.
function UploadFisier($file, $sufix, $target_dir, $maxsize)
{
try {
// your code
} catch (\Exception $e) {
echo $e->getMessage();
die();
}
}