How to remove duplicates from php two-dimensional array

In PHP, a two-dimensional array refers to an array containing multiple arrays, that is, the elements in the array are arrays, and its form is as follows:

$students = array(
    array('id' => 1, 'name' => '张三', 'age' => 18),
    array('id' => 2, 'name' => '李四', 'age' => 19),
    array('id' => 3, 'name' => '王五', 'age' => 20),
    array('id' => 4, 'name' => '张三', 'age' => 18)
);

In a two-dimensional array, we may encounter To duplicate elements, in this case, we need to remove the duplicates. So, how to remove weight?

Method 1: Use the array_unique function

The array_unique function can remove duplicate values ​​​​in the array, but it can only be used for one-dimensional arrays, so it needs to be processed on the two-dimensional array. The specific idea is as follows:

We can traverse each subarray in the two-dimensional array, convert it to a string, and save it to a new array. Then, the new array is deduplicated, and the final result is a deduplicated two-dimensional array.

The code is implemented as follows:

function unique_array($array) {
    $temp = array();
    foreach ($array as $key => $value) {
        $temp[$key] = implode(',', $value);
    }
    $temp = array_unique($temp);
    $result = array();
    foreach ($temp as $key => $value) {
        $result[$key] = explode(',', $value);
    }
    return $result;
}

$students = array(
    array('id' => 1, 'name' => '张三', 'age' => 18),
    array('id' => 2, 'name' => '李四', 'age' => 19),
    array('id' => 3, 'name' => '王五', 'age' => 20),
    array('id' => 4, 'name' => '张三', 'age' => 18)
);

$result = unique_array($students);
print_r($result);

The output result is as follows:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => 张三
            [age] => 18
        )

    [1] => Array
        (
            [id] => 2
            [name] => 李四
            [age] => 19
        )

    [2] => Array
        (
            [id] => 3
            [name] => 王五
            [age] => 20
        )

)

Method 2: Use array_reduce function

array_reduce function can merge two-dimensional arrays into one dimension array and perform deduplication operations on it. The specific idea is as follows:

We can first convert each sub-array in the two-dimensional array into a string and save it to a new array. Then, use the array_reduce function to combine the new arrays into a string, and use the array_unique function to deduplicate the string. Finally, use the explode function to convert the deduplicated string into a two-dimensional array.

The code is implemented as follows:

function unique_array($array) {
    $temp = array();
    foreach ($array as $key => $value) {
        $temp[$key] = implode(',', $value);
    }
    $result = array_reduce($temp, function($carry, $item){
        if (!in_array($item, $carry)) {
            $carry[] = $item;
        }
        return $carry;
    }, array());
    $result = array_map(function($item) {
        return explode(',', $item);
    }, $result);
    return $result;
}

$students = array(
    array('id' => 1, 'name' => '张三', 'age' => 18),
    array('id' => 2, 'name' => '李四', 'age' => 19),
    array('id' => 3, 'name' => '王五', 'age' => 20),
    array('id' => 4, 'name' => '张三', 'age' => 18)
);

$result = unique_array($students);
print_r($result);

The output results are as follows:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => 张三
            [age] => 18
        )

    [1] => Array
        (
            [id] => 2
            [name] => 李四
            [age] => 19
        )

    [2] => Array
        (
            [id] => 3
            [name] => 王五
            [age] => 20
        )

)

Summary

The above are the two methods of deduplication of two-dimensional arrays in PHP. Both methods use PHP's built-in functions, and the specific implementation ideas are relatively simple. It should be noted that when using the array_reduce function, you need to use the array_map function to convert the deduplicated string into a two-dimensional array.

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