is_countable() would demand PHP >= 7.3.0 as of which it is available.
See https://www.php.net/manual/en/function.is-countable.php
Use a polyfill for PHP < 7.3.0
Loading serendipity_admin.php with $serendipity['production'] = false
yielded a red alert box:
The Serendipity JavaScript-library could not be loaded. This can happen
due to PHP or Plugin errors, or even a malformed browser cache. To check
the exact error please open
https://.../index.php?/plugin/admin/serendipity_editor.js manually in
your browser and check for error messages.
Where at the end of that file could be found:
== ERROR-REPORT (BETA/ALPHA-BUILDS) ==
<p><b>Warning:</b> count(): Parameter must be an array or an object that
implements Countable in
plugins/serendipity_event_linktrimmer/serendipity_event_linktrimmer.php
on line 323.</p>
Iconfont icons are of no value to screenreader users; in our case,
they get alternative text. By adding 'aria-hidden="true"' to the
<span> holding the iconfont icon, we avoid the screenreader trying
to announce the iconfont icon.
This commit is to ensure consistency with the core across the
additional_plugins repository. While I was at it, I also cleaned
up the ChangeLogs, trying to establish a common pattern.
because of ReferenceError: jQuery is not defined with
jQuery(function() {
jQuery('input[type="url"]').change(function() {
if (this.value != '' && ! (this.value.substr(0,7) == 'http://' || this.value.substr(0,8) == 'https://')) {
this.value = 'http://' + this.value;
}
});
})
This is specific to netzgestaltung. I dont have that issue.