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Grav
Modern, Crazy Fast, Ridiculously Easy and Amazingly Powerful Flat-File CMS powered by PHP, Markdown, Twig, and Symfony
Drupal definitely is the 800lb gorilla in the PHP space. You can do everything with it, but you'll often need to spend some (read: lots of) time getting it going.
For lighter sites, I recommend GravCMS [1], which does a fair amount of what you're looking for. Their documentation [2] is decent, as well.
How many users does your client have? It's been a while since I last played in the WP land, but is it possible to setup new roles that are more restricted?
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.