Convert array of array of sentence words into flare.json format

In PHP I’m trying to convert some sentences into a nested structure of words, like that used for some D3.js tree diagrams, such as this, often called flare.json.

I have the sentences as an array of arrays (in reality they’d all be different lengths):

$sentences = [
    ["The", "best", "thing"],
    ["The", "best", "place"],
    ["The", "nice", "thing"],
    ["A", "nice", "thing"]
];

And want to end up with a nested array structure like this:

$flare = [ 
    [ 
        "name" => "The",
        "children" => [
            [
                "name" => "best",
                "children" => [
                    [
                        "name" => "thing"
                    ],
                    [
                        "name" => "place"
                    ],
                ],
            ],
            [ 
                "name" => "nice",
                "children" => [ 
                    [ 
                        "name" => "thing"
                    ] 
                 ]
            ],
        ] 
    ],
    [ 
        "name" => "A",
        "children" => [
            [
                "name" => "nice",
                "children" => [
                    [
                        "name" => "thing"
                    ] 
                ] 
            ] 
        ] 
    ]
];

But my brain is failing when I try to work out how to iterate through and construct that structure.

Answer

Okay this task in challenging because we need to iterate every word in their level of tree. I write recursive way to do this task

function put_word($flare, $sentence, $level) {
    // check if there are name exists
    for($i = 0; $i<count($flare); $i++) {
        if($flare[$i]["name"] == $sentence[$level]) {
            // check if this is last word
            if($level == count($sentence)-1) {
                return $flare;
            }
            // if found, add their children
            if(!array_key_exists("children", $flare[$i])) {
                $flare[$i]["children"] = [];
            }
            $flare[$i]["children"] = put_word($flare[$i]["children"], $sentence, $level + 1);
            return $flare;
        }
    }
    // if not found, add new array
    $flare[] = [
        "name" => $sentence[$level],
    ];
    $last = count($flare) - 1;
    // stop criteria
    if($level == count($sentence) - 1) {
        return $flare;
    } else {
        $flare[$last]["children"] = put_word([], $sentence, $level + 1);
        return $flare;
    } 
}

so you can just call the function with array of words

$sentences = [
    ["The", "best", "thing"],
    ["The", "best", "place"],
    ["The", "nice", "thing"],
    ["A", "nice", "thing"]
];

$flare = [];

foreach($sentences as $sentence) {
    $flare = put_word($flare, $sentence, 0);
}

and this is the output

[
  {
    "name": "The",
    "children": [
      {
        "name": "best",
        "children": [
          {
            "name": "thing"
          },
          {
            "name": "place"
          }
        ]
      },
      {
        "name": "nice",
        "children": [
          {
            "name": "thing"
          }
        ]
      }
    ]
  },
  {
    "name": "A",
    "children": [
      {
        "name": "nice",
        "children": [
          {
            "name": "thing"
          }
        ]
      }
    ]
  }
]