Deprecated: Use of "self" in callables is deprecated

[siMobin]

How I fix this issue?

Deprecated: Use of "self" in callables is deprecated in 
E:\Stamford University Bangladesh\vendor\erusev\parsedown-extra\ParsedownExtra.php 
on line 397

Note

Don't tell me to use error_reporting(E_ALL & ~E_DEPRECATED);

version Info:

    "erusev/parsedown": "^1.7",
    "erusev/parsedown-extra": "^0.8.1"

My code

<?php
require_once($_SERVER['DOCUMENT_ROOT'] . '/conn.php');
require($_SERVER['DOCUMENT_ROOT'] . '/vendor/autoload.php');
// error_reporting(E_ALL & ~E_DEPRECATED);

// Create an instance of Parsedown
$parsedown = new ParsedownExtra();
//.
//.
//.
//.
   <p>
                <?php
                // Parse Markdown content
                $parsedContent = $parsedown->text($row['content']);
                echo $parsedContent;
                ?>
  </p>
  
.....................................
...................................
........................................

[jurgen178]

In line #511, change it to
uasort($this->DefinitionData['Footnote'], array($this, 'sortFootnotes'));

'self::sortFootnotes' is a string in the uasort() function. In modern PHP, this should use an array callable format.