<?php
$characters = [
    "Negan" => [
        "city" => "The Sanctuary",
        "weapon" => "Lucille"
    ],
    "Daryl" => [
        "city" => "Alexandria",
        "weapon" => "crossbow"
    ],
    "Ezekiel" => [
        "city" => "The Kingdom",
        "weapon" => "Shiva"
    ]
];
$characters ["Estev"]["city"] = "Bordeaux";
$characters ["Estev"]["weapon"] = "Lance-flamme";
var_dump($characters);
?>