Convert .HEIC to .JPG with ImageMagick in PHP

I am looking to try and create a small image converter that would convert HEIC files that are uploaded to a php web document to .JPG (or any other generic file format).

I am running PHP off a unix server and have ImageMagick installed on the server. The following command line code works from the server:

mogrify -format jpg *.HEIC

I’d like to convert this command line code to PHP.

As mentioned I like to convert the command line formatting code to PHP. I currently have the following code set up in a basic HTML + PHP form. The file being converted is newly uploaded and not located on the server. If necessary I can upload to the server first then read form the server file.

if($_SERVER["REQUEST_METHOD"] == "POST")
{
    if(empty($_FILES['image_url']['name']))
    {
        echo "No File uploaded";
    }
    else{

        $uploadedImage = fopen($_FILES['image_url']['tmp_name'], 'rb');

        $image_to_convert = new Imagick();
        $image_to_convert->readImageFile($uploadedImage);
        $image_to_convert->setFormat("jpg");

        $image_to_convert->setFileName('test.jpg');

        header('Content-Type: image/jpg');
        header('Content-disposition: attachment; filename='.$image_to_convert->getFileName());
        header("Content-Description: File Transfer"); 

        readfile($image_to_convert);
    }
}

This code downloads a "test.jpg" file, but when I try to open it in Windows image viewer it displays a "It looks like we don’t support this file format" message. I’m relatively new to PHP so I don’t know all the tricks for output/input streams so if my code is horrible let me know.

Any and all help is welcome. Thanks!