A protected page returns an object/map/dictionary/associative array for the 'protection' property:
http://en.wikipedia.org/w/api.php?action=mobileview&page=Barack_Obama&prop=protection|editable&format=json
{"mobileview":{"sections":[],"protection":{"edit":["autoconfirmed"],"move":["sysop"]},"editable":false}}
But an unprotected page seems to return an empty array instead of an object:
http://en.wikipedia.org/w/api.php?action=mobileview&page=Katakana&prop=protection|editable&format=json
{"mobileview":{"sections":[],"protection":[],"editable":true}}
PHP may consider those the same type, but JSON/JavaScript, Java, Objective-C, etc consider them distinct types and we should be consistent in output to avoid surprises in the clients.
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