Fatal error: Uncaught TypeError: usort(): Argument #2 ($callback) must be a valid callback, function "cmp" not found or invalid function name in /home/tiger56/public_html/author.php:98 Stack trace: #0 /home/tiger56/public_html/author.php(98): usort(Array, 'cmp') #1 {main} thrown in /home/tiger56/public_html/author.php on line 98