Resize copied image on upload as thumbnail

[Russia]

I am working on an uploader and slowly getting it working, I am uploading 3 images at once, and setting arrays for each one as keys, with an increment of ++1. I am wanting to resize the image before it gets copied to the thumbnail folder.

I have this code.

<?php
if (isset($_POST['addpart'])) {

    $image = $_FILES['images']['tmp_name'];
    $name  = $_POST['username'];
    $i     = 0;
    foreach ($image as $key) {

        $fileData   = pathinfo(basename($_FILES["images"]["name"][$i]));
        $fileName[] = $name . '_' . uniqid() . '.' . $fileData['extension'];
        move_uploaded_file($key, "image/" . end($fileName));

    //get uploaded file info before we proceed with resize
    $image_name = $_FILES['images']['name'][$i]; //file name
    $image_size = $_FILES['images']['size'][$i]; //file size
    $image_temp = $_FILES['images']['tmp_name'][$i]; //file temp
    $image_size_info    = getimagesize($image_temp); //gets image size info from valid image file


        copy("image/" . end($fileName), "image_thumbnail/" . end($fileName));
        $i++;
    }
    echo 'Uploaded<br>';
    echo 'Main Image - ' . $fileName[0] . '<br>';
    echo 'Extra Image 1 - ' . $fileName[1] . '<br>';
    echo 'Extra Image 2 - ' . $fileName[2] . '<br>';
    echo '<hr>';

}
?>

Everything works with it. As you see, I started on getting the file info, but after that I am totally stuck on what to do after to resize the image proportionally with a maximum width of xPX and height to match it without looking distorted.

Any help would be really appreciated. Thank You.