phpcms切换到php7.2后没法修改文章提示Uncaught Error: [] operator not supported for strings

　　前段时间将客户的phpcms站点升级到php7.2，相对比较顺利，可是今天他反应文章没法修改了，提示Uncaught Error: [] operator not supported for strings 错误，这就有点尴尬了，多是PHP7以上对语法要求比较严谨，那咱们就照着错误提示来寻找解决方案

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

　　打开/phpcms/modules/admin/classes/push_api.class.php，大概在约 141行，

$fields_arr = $fields_value = '';

　　将它改成

$fields_arr = $fields_value = [];

　　保存，上传，覆盖文件，从新编辑一下文章看看，此次果真能够了