Check if a pear key is present in PHP

Apologies for the newbie question but I'm relatively new to PHP and want to do something fairly simple... If I have an array of keys & values (pears):

$arrayOfPears = array(
                      "Green Anjou" => [ 7,
                                         "plump",
                                         "ripe",
                                         "juicy",
                                         "green"
                                        ],
                      "Bartlett"     => [ 2,
                                          "moderately plump",
                                          "unripe",
                                          "sweet",
                                          "greeny-yellow"
                                         ],
                      "Comice"       =>  [ 3,
                                           "rather plump",
                                           "ripe",
                                           "blinding",
                                           "deep-green"
                                         ],
                      "Plum"          => [ 6,
                                           "rotund",
                                           "over-ripe",
                                           "sweet",
                                           "purple",
                                           "not really a pear, as far as I'm aware"
                                          ]
                      );

I am able to access a specific pear's value and use it for a comparison operation. For example:

if($arrayofPears['Comice'][2] == "ripe") {
   $nibble = true;
   return $nibble;
}

Does return a true $nibble. However, what I would like to be able to do is check first if the Comise key is present in the array, before I try to enter the if statement and find out if I get a true $nibble.

So... how do I check if any 'Comice' are present in this situation, before committing myself to enter the conditional?