Resizing and moving an image - php

Question

I'm kind of a beginner in PHP and here's what I'm trying to do:
Recieve an uploaded image and move it to temp/ folder
Examine it and decide whether it needs to be resized or not (it needs, if it's not 135px wide)
If needs to be resized, resize it and save as results/{number}_cover.jpg
If it doesn't, copy an uploaded image right away to the same place, without resizing
And here's my code:
$target_path = "temp/";
$target_path = $target_path . basename($_FILES["file" . $a]["name"]);
move_uploaded_file($_FILES["file" . $a]["tmp_name"], $target_path);
list($current_width, $current_height, $type, $attr) = getimagesize($target_path);
if($current_width != 135) {
$filename = $a . "_cover.jpg";
$result_image = "results/" . $filename;
$writing = fopen($result_image, 'w');
$scale = (135 / $current_width);
$new_width = 135;
$new_height = $current_height * $scale;
$result_image = imagecreatetruecolor($new_width, $new_height);
$current_image = imagecreatefromjpeg($target_path);
imagecopyresampled($result_image, $current_image, 0, 0, 0, 0, $new_width, $new_height, $current_width, $current_height);
imagejpeg($result_image, null, 100);
fclose($writing);
} else {
$target_path = "results/";
$target_path = $target_path . $a . "_cover.jpg";
move_uploaded_file($_FILES["file" . $a]["tmp_name"], $target_path);
}
However, this is what this code does for me:
1. If an image needs resizing, it just give me an image data to the browser instead of saving it to the file
2. If it doesn't need resizing, nothing happens.
What am I doing wrong?
Thanks in advance for your help!