phpcms切换到php7.2版本后无法修改文章提示Uncaught Error: [] o

　　我们使用phpcms建站时，有时候将phpcms站点升级到php7.2会出现文章无法修改了，提示Uncaught Error: [] operator not supported for strings 错误，可能是PHP7以上对语法要求比较严谨，以下青锋建站就照着错误提示来和大家寻找解决方案。

Fatal error: Uncaught Error: [] operator not supported for strings in
*****/phpcms/modules/admin/classes/push_api.class.php:145 Stack trace: #0
*****/phpcms/modules/admin/classes/push_api.class.php(50): push_api->position_list(Array, Array, 0, 'content_model') #1
*****/caches/caches_model/caches_data/content_update.class.php(62): push_api->position_update(4, 1, 14, Array, Array, 0) #2
*****/caches/caches_model/caches_data/content_update.class.php(18): content_update->posid('posids', Array) #3
*****/phpcms/model/content_model.class.php(303): content_update->update(Array) #4
*****/phpcms/modules/content/content.php(221): content_model->edit_content(Array, 4) #5
*****/phpcms/libs/classes/application.class.php(31): content->edit() #6
*****/phpcms/libs in
*****/phpcms/modules/admin/classes/push_api.class.php on line 145
 

$fields_arr = $fields_value = '';

$fields_arr = $fields_value = [];