how check php array associative sequential?

php treats arrays associative, there aren't any built functions. anyone advise sincerely fit proceed check an array contains wholly numeric keys?

basically, i wish means compute between this:

$sequentialarray = array('apple', 'orange', 'tomato', 'carrot');

and this:

$assocarray = array('fruit1' => 'apple', 
                    'fruit2' => 'orange', 
                    'veg1' => 'tomato', 
                    'veg2' => 'carrot');