To get a column from a multidimensional PHP array, the most common method is to use the array_column() function. 1. array_column() is suitable for two-dimensional arrays, such as extracting the name column in $users: $names = array_column($users, 'name'); 2. You can specify the key name to retain the original field, such as using id as the key: $names = array_column($users, 'name', 'id'); 3. For three-dimensional and above arrays, you need to manually extract it with array_map, such as taking $info['name'] in $data: $names = array_map(fn($item) => $item'info', $data); 4. Fault-tolerant treatment should be performed when encountering irregular structures, such as filtering empty values: $names = array_filter(array_column($data, 'name')) or set the default value: $names = array_map(fn($item) => $item['name'] ?? 'Unknown', $data).

The most common method to get a column from a multidimensional PHP array is to use array_column() function. This function is specifically used to extract a column of data in a two-dimensional array, which is very convenient.

Use array_column() to extract the specified column

This is the most direct and recommended way. Suppose you have an array similar to the following:

 $users = [
    ['id' => 1, 'name' => 'Alice', 'email' => 'alice@example.com'],
    ['id' => 2, 'name' => 'Bob', 'email' => 'bob@example.com'],
    ['id' => 3, 'name' => 'Charlie', 'email' => 'charlie@example.com'],
];

If you want to extract name column of all users, you can write it like this:

 $names = array_column($users, 'name');

The result is:

 ['Alice', 'Bob', 'Charlie']

• The first parameter is the array you want to process
• The second parameter is the "column name" (that is, the key name) you want to extract

If you also want to keep a field in the original array as the key of the new array, such as using id as the key:

 $names = array_column($users, 'name', 'id');

The result will be:

 [
    1 => 'Alice',
    2 => 'Bob',
    3 => 'Charlie'
]

This approach is suitable for most cases of two-dimensional arrays.

What to do with more than two-dimensional arrays?

If the array is nested more than two layers (such as three-dimensional or higher), array_column() is not enough. At this time, you need to manually traverse or cooperate with other functions to extract the data.

For example:

 $data = [
    [
        'id' => 1,
        'info' => ['name' => 'Alice', 'age' => 25]
    ],
    [
        'id' => 2,
        'info' => ['name' => 'Bob', 'age' => 30]
    ]
];

If you want to extract the name field under info in each element, you can do it like this:

 $names = array_map(function($item) {
    return $item['info']['name'];
}, $data);

The result is:

 ['Alice', 'Bob']

Although this writing method is slightly more complicated than array_column() , it is clear in logic and is suitable for handling arrays with deeper structures.

What should I do if I encounter irregular structures?

Sometimes the array structure may be less unified, for example, some levels lack the expected key, so you need to pay attention to prevent errors.

for example:

 $data = [
    ['id' => 1, 'name' => 'Alice'],
    ['id' => 2], // Missing name field['id' => 3, 'name' => 'Charlie']
];

At this time, if you use array_column($data, 'name') directly, the second element will return null . You can combine array_filter() to filter out null values:

 $names = array_filter(array_column($data, 'name'));

This way, only the item with name can be retained.

If you want to provide default values ??when missing, you can use array_map to customize the processing:

 $names = array_map(function($item) {
    return $item['name'] ?? 'Unknown';
}, $data);

Let's summarize

• array_column() is the easiest way to extract a column in a two-dimensional array
• For three-layer or above structures, manual extraction is required using array_map
• When encountering a situation where the structure is not unified, remember to do fault tolerance to avoid errors

Basically these methods are just the ones, not complicated but are easy to ignore some boundary situations.

The above is the detailed content of how to get a column from a multidimensional php array. For more information, please follow other related articles on the PHP Chinese website!