I recently migrated my Drupal 7 sites to A2 Hosting. Everything was working fine, until I had to edit a node which had some simple PHP code content in its body (it only shows different links if the user is anonymous or authenticated).
After modifying the content and clicking on Save, the page reloads without giving any message (such as node was updated), showing the content editing form as it was prior to the editing.
If I try to create a new page whose body is formatted as PHP code, the page is reloaded with a blank form after I hit Save.
Despite this, all my previous, unmodified PHP snippets were working fine.
This happens in 3 Drupal 7 sites I have hosted at A2. In one of them, as an attempt to fix the issue, I tried to temporary disable the PHP filter module and re-enable it afterwards. I managed to disable it, but it cannot be re-enabled. Every node and block using that input filter stopped working.
Then I installed a new, clean, standard Drupal 7.74 site on a subdomain, for testing purposes. It is impossible to enable PHP filter module in it. If I try it in admin/modules, the page reloads without any message and the PHP filter module remains disabled, just like in my own site. It is possible to enable any other modules, but PHP filter.
What could be the problem?