PHP two-dimensional number combination does not remove duplicates

In PHP, we often need to use arrays, and we often need to merge arrays, such as merging two arrays into one array, or merging multiple arrays into one array. When it comes to merging two-dimensional arrays, we may encounter a problem, that is, the merged array will not automatically deduplicate. This article will introduce the problem and solution of PHP two-dimensional number combination without deduplication.

1. What is a two-dimensional array

In PHP, an array is a very important data structure. It is a collection of data, and each data has a corresponding key. value and index. A two-dimensional array is an array nested within another array, that is, each element is an array.

2. Two-dimensional array in PHP

In PHP, there are two ways to represent two-dimensional arrays, one is to use the array() function, and the other is to use the [] syntax Sugar, here is an example to illustrate:

// 使用array()函数表示二维数组
$students = array(
    array('name' => '张三', 'age' => 18),
    array('name' => '李四', 'age' => 19),
    array('name' => '王五', 'age' => 20)
);

// 使用[]语法糖表示二维数组
$students = [
    ['name' => '张三', 'age' => 18],
    ['name' => '李四', 'age' => 19],
    ['name' => '王五', 'age' => 20]
];

3. Merging of two-dimensional arrays in PHP

PHP provides the array_merge() function for merging arrays. This function can merge multiple arrays. Return a new array, the sample code is as follows:

$students1 = [
    ['name' => '张三', 'age' => 18],
    ['name' => '李四', 'age' => 19],
    ['name' => '王五', 'age' => 20]
];

$students2 = [
    ['name' => '赵六', 'age' => 21],
    ['name' => '孙七', 'age' => 22],
];

$students = array_merge($students1, $students2);

print_r($students);

The output result is as follows:

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

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

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

    [3] => Array
        (
            [name] => 赵六
            [age] => 21
        )

    [4] => Array
        (
            [name] => 孙七
            [age] => 22
        )

)

We can see that using the array_merge() function can easily merge two arrays into one array . However, when there are duplicate elements in the merged array, the merged array will not be automatically deduplicated, as shown below:

$students1 = [
    ['name' => '张三', 'age' => 18],
    ['name' => '李四', 'age' => 19],
    ['name' => '王五', 'age' => 20]
];

$students2 = [
    ['name' => '李四', 'age' => 19],
    ['name' => '孙七', 'age' => 22],
];

$students = array_merge($students1, $students2);

print_r($students);

The output result is as follows:

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

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

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

    [3] => Array
        (
            [name] => 李四
            [age] => 19
        )

    [4] => Array
        (
            [name] => 孙七
            [age] => 22
        )

)

We can see It turns out that there are two duplicate elements in the merged array [name => '李思', age => 19].

4. Solution to the problem that PHP two-dimensional number combination does not remove duplicates

In order to solve the problem that PHP two-dimensional number combination does not remove duplicates, we can use the array_unique() function. This function can be used to remove duplicate elements from an array and return a new non-duplicate array.

The sample code is as follows:

$students1 = [
    ['name' => '张三', 'age' => 18],
    ['name' => '李四', 'age' => 19],
    ['name' => '王五', 'age' => 20]
];

$students2 = [
    ['name' => '李四', 'age' => 19],
    ['name' => '孙七', 'age' => 22],
];

$students = array_merge($students1, $students2);
$students = array_unique($students, SORT_REGULAR);

print_r($students);

The output result is as follows:

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

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

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

    [4] => Array
        (
            [name] => 孙七
            [age] => 22
        )

)

We can see that using the array_unique() function can easily merge the merged arrays. Finally, Get an array without duplicate elements.

5. Summary

This article introduces the problem and solution of PHP two-dimensional number combination without deduplication. Through the explanation of this article, we can know that although it is very convenient to use the array_merge() function Merge arrays, but when it comes to two-dimensional arrays, the merge will not automatically deduplicate. You need to use the array_unique() function to deduplicate to get a new array without duplication.

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