Copy and Paste plugin full

<?php
/*
Plugin Name: Copy and Paste Add-on
Plugin URI: N/A
Description: Adds on text to any copy and paste which backlinks to the specified site.
Original Code for Plugin Template: http://wpmu.org/how-to-create-your-own-super-simple-wordpress-plugins/
Original Code for Copy and Paste: http://www.wpbeginner.com/wp-tutorials/how-to-add-a-read-more-link-to-copied-text-in-wordpress/
Version: 1.0
Author: Tzvi Joffre
Author URI: N/A
License: GPL2
*/

if (is_single()) { ?>

<script type='text/javascript'>
function addLink() {
    if (
window.getSelection().containsNode(
document.getElementsByClassName('entry-content')[0], true)) {
    var body_element = document.getElementsByTagName('body')[0];
    var selection;
    selection = window.getSelection();
    var oldselection = selection
    var pagelink = "<br /><br /> Read more: <?php the_title(); ?> <a href='<?php echo get_permalink(get_the_ID()); ?>'><?php echo get_permalink(get_the_ID()); ?></a>"; //Change this if you like
    var copy_text = selection + pagelink;
    var new_div = document.createElement('div');
    new_div.style.left='-99999px';
    new_div.style.position='absolute';

    body_element.appendChild(new_div );
    new_div.innerHTML = copy_text ;
    selection.selectAllChildren(new_div );
    window.setTimeout(function() {
        body_element.removeChild(new_div );
    },0);
}

document.oncopy = addLink;
</script>

<?php
}
}

add_action( 'wp_head', 'add_copyright_text'); ?>