WordPress widget to fetch and display YOURLS shorturl

YWP_widget.php

<?php 
/*
Name: YOURLS WordPress Widget
Description: A WordPress widget to display a YOURLS shorturl and QR code
Code URI: https://gist.github.com/joshp23/3f990e6ec36e24ba53985968bbfa89f1
Author: Josh Panter
Author URI: https://unfettered.net
======================================================================
This widget will create &/or fetch the existing short URL for a WordPress post from YOURLS,
provide a button to copy the short url, and optionally display a qrcode.

In YOURLS:
Install the "Change error messages" plugin
https://github.com/adigitalife/yourls-change-error-messages

Optional: For QR code display
Install and configure IQRCodes (and U-SRV)
https://github.com/joshp23/YOURLS-IQRCodes
https://github.com/joshp23/YOURLS-U-SRV

In WordPress:
Install the "Enable Shortcode and PHP in Text widget" plugin and enable PHP evaluation in settings
https://wordpress.org/plugins/enable-shortcode-and-php-support-in-text-widget/

Create a new text widget with the following code, adjsuted to suit your needs, and restrict visibility to "posts".
======================================================================
Copyright (C) 2018 Josh Panter

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
======================================================================
*/ 
  $api_url  = 'https://sho.rt/yourls-api.php';
  $sig      = 'YOUR_SIGNATURE';
  
  /* Do not edit below this line */
  
	$url = get_permalink(); 
	$args = array( 
				'action' => 'shorturl', 
				'url' => $url,
				'format' => 'json',
				'signature' => $sig
	);
	$ch = curl_init();
		curl_setopt($ch, CURLOPT_URL, $api_url);
		curl_setopt($ch, CURLOPT_HEADER, 0);
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($ch, CURLOPT_POST, 1);
		curl_setopt($ch, CURLOPT_POSTFIELDS, $args);
	$data = curl_exec($ch);
		curl_close($ch);
	$data = json_decode( $data, true );

	$short = $data['shorturl'];
	$qr = $data['qrcimg'] ? ' <img style="-webkit-filter: drop-shadow(5px 5px 5px #222); filter: drop-shadow(5px 5px 5px #222); max-width: 128px;" src="'.$data['qrcimg'].'" />' : null;
?>

<div style="text-align: center;">
	<div id="short">
		<?php echo $short ?>
	</div>
	<button onclick="copyMe()">Copy URL</button>
	<br>
	<?php echo $qr ?> 
</div>
<script>
	function copyMe() {
		if (document.selection) { 
			var range = document.body.createTextRange();
			range.moveToElementText(document.getElementById("short"));
			range.select().createTextRange();
			document.execCommand("copy"); 
			alert("Copied: " + range);
		} else if (window.getSelection) {
			var range = document.createRange();
			range.selectNode(document.getElementById("short"));
			window.getSelection().addRange(range);
			document.execCommand("copy");
			alert("Copied: " + range);
	}
}
</script>

This seems to keep re-generating new QR codes on the server, causing the cache folder to grow considerably. Also, for some reason, image eventually stops showing (I guess due to 1 min hot linking on SRV-U).. What is the solution for fixing this?

My WordPress site is using cache, and the image is cached too.. but cannot be loaded, as it ends up saying "FAIL: bad access key"a.