Uploading image files and php not registering any inputs [on hold]

I have a fairly simple HTML form with a file input and I'm trying to post it to a block of PHP code.

I use this same method in other places on my website and it works perfectly, there must be some very basic (probably embarrassing) thing I'm overlooking or don't understand.

**I have a functioning method call (upload_image) and that method works, that's not the issue. The issue is in the html form being read by the php code above it.

HTML & PHP:

<?php 

        echo 'It reads to this point';

        if(empty($_FILES['aca']))
            print_r("Damn");
        if(isset($_FILES['aca']) === true)
        {
            echo 'something';
            if(empty($_FILES['aca']['name']) === true)
            {
            echo 'Please choose a file! <br>';
            }
            else
            {

                $allowed = array('jpg', 'jpeg', 'gif', 'png');

                $file_name = $_FILES['aca']['name']; 

                $file_extn = strtolower(end(explode('.', $file_name)));
                $file_temp = $_FILES['aca']['tmp_name'];
                echo '<br>';
                echo '<br>';
                print_r($_FILES['aca']['tmp_name']);
                echo '<br>';
                echo '<br>';
                if(in_array($file_extn, $allowed) === true) {

                upload_image($file_temp,$file_extn);

                echo 'You have uploaded a picture!';
                echo '<b><h3>Press submit again to finish the upload</h3></b>';
                //echo "<script>window.top.location='../hidden/viewPNM.php?id=$permi'</script>";


                }
                else
                {
                echo 'Incorrect File Type!! <br> Allowed: ';
                echo implode(', ', $allowed);

                }

            }

        }


        ?>
        <form action="" method="post" id="aca" enctype="multipart/form-data">
        <input type="file" id="aca" name="aca"> <input type="submit">
        </form>