Fatal error: Uncaught TypeError: usort(): Argument #1 ($array) must be of type array, null given in /home/ldwaorg/public_html/maps/list_maps.php:88 Stack trace: #0 /home/ldwaorg/public_html/maps/list_maps.php(88): usort(NULL, 'publications_so...') #1 {main} thrown in /home/ldwaorg/public_html/maps/list_maps.php on line 88