How to convert a one-dimensional array into a three-layer nested tree structure using PHP?

This article discusses how to efficiently convert PHP 1D arrays into three-layer nested tree structures. Given an array containing project name, model, and location information, the goal is to convert it into a tree structure, with the project name as a first-level node, the model as a second-level node and the location as a third-level node.

Initial array:

 $arr = [
    ['name' => "Project 1", 'model' => "Gold", 'location' => 'Suzhou'],
    ['name' => "Project 1", 'model' => "Silver", 'location' => 'Shanghai'],
    ['name' => "Project 2", 'model' => "Copper", 'location' => 'Beijing'],
    ['name' => "Project 2", 'model' => "Copper", 'location' => 'Shenzhen'],
];

Target tree structure:

 $target = [
    [
        'name' => "item 1",
        'child' => [
            ['model' => "Gold", 'child' => [['location' => 'Suzhou']]],
            ['model' => "Silver", 'child' => [['location' => 'Shanghai']]],
        ]
    ],
    [
        'name' => "Project 2",
        'child' => [
            ['model' => "Copper", 'child' => [['location' => 'Beijing'], ['location' => 'Shenzhen']]],
        ]
    ],
];

The previous solution was too complicated. We can use a simpler and easier to understand method to build a tree-like structure using loops and conditional judgments:

 $result = [];
foreach ($arr as $item) {
    $name = $item['name'];
    $model = $item['model'];
    $location = $item['location'];

    // Find or create project name node $nameIndex = array_search($name, array_column($result, 'name'));
    if ($nameIndex === false) {
        $result[] = ['name' => $name, 'child' => []];
        $nameIndex = count($result) - 1;
    }

    // Find or create model node $modelIndex = array_search($model, array_column($result[$nameIndex]['child'], 'model'));
    if ($modelIndex === false) {
        $result[$nameIndex]['child'][] = ['model' => $model, 'child' => []];
        $modelIndex = count($result[$nameIndex]['child']) - 1;
    }

    // Add location node $result[$nameIndex]['child'][$modelIndex]['child'][] = ['location' => $location];
}

print_r($result); // output the converted tree structure

This code first initializes an empty array $result . It then iterates over each item in the original array $arr . For each project, it looks for the presence of the corresponding project name and model node. If it does not exist, a new node is created. Finally, it adds the location information under the corresponding model node. This method is clearer and easier to maintain.

This approach avoids nested array_map and array_reduce , making it easier to understand and debug. It operates directly on arrays and is more efficient. Choose the method that suits your project and adjust the code according to actual conditions.

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