Drupal.org already has a few issues similar to this. The ones I've read blame the simpletest module. This one is not caused by simpletest so I don't think it's a duplicate.
In my case I'm seeing this on Drupal's status report page. The reason is that _system_sort_requirements() expects an array with a title string, i.e. $b['title'] = 'some string'. Instead, $b contains something more like this:
... (Array, 4 elements) title (Array, 2 elements) 0 (String, 31 characters ) Grammar Parser PHP memory limit 1 (String, 31 characters ) Grammar Parser PHP memory limit value (Array, 2 elements) 0 (String, 3 characters ) 48m 1 (String, 3 characters ) 48m
Title is an array instead of a string, but the real problem is Drupal has run out of memory. Either $a or $b contain arrays like this where Grammar Parser announces either memory or time limit problems.
I imagine this issue will quickly be resolved as won't fix, not a bug; i.e. that it is user error trying to run Drupal with so little memory available. But please consider that Drupal should present a reasonable error message in this case. Very few people will figure out that strcmp() error actually means they need to increase memory limits or upgrade hosting plans (or switch to Wordpress). Especially the status report page should be able to inform a user of this problem.