Use the array_merge() function to merge multiple arrays

In PHP programming, we often need to merge multiple arrays, especially when dealing with large data. If you manipulate each array manually, it's easy to overlook some of its elements and end up with errors. If you use the array_merge() function, you can merge arrays more easily and reduce potential errors. This article will introduce how to use the array_merge() function to merge multiple arrays.

1. Introduction to the array_merge() function

The array_merge() function is a built-in function of PHP, which can merge one or more arrays into a new array in a specified order. It will use the value of each array as the value of the new array, and the key name will be determined based on the original array.

$array1 = array('a', 'b', 'c');
$array2 = array(1, 2, 3);
$result = array_merge($array1, $array2);
print_r($result);

The above code will output the following results:

Array
(

[0] => a
[1] => b
[2] => c
[3] => 1
[4] => 2
[5] => 3

)

As can be seen from the output results, the elements of $array1 and $array2 are sequentially merged into the $result array.

2. Use the array_merge() function to merge multiple arrays

When you need to merge multiple arrays, you can use the array_merge() function to achieve it. For example, we have three arrays that can be combined like this:

$array1 = array('a', 'b', 'c');
$array2 = array(1, 2, 3 );
$array3 = array('x', 'y', 'z');
$result = array_merge($array1, $array2, $array3);
print_r($result);

The above code will output the following results:

Array
(

[0] => a
[1] => b
[2] => c
[3] => 1
[4] => 2
[5] => 3
[6] => x
[7] => y
[8] => z

)

As you can see, the elements in the three arrays are Merged into the $result array, and the order of the original array is preserved. If there are the same key names, the values ​​in the latter array will overwrite the values ​​in the previous array.

3. Merge associative arrays

The array_merge() function can merge associative arrays, but it should be noted that if there are duplicate key names, the values ​​in the latter array will overwrite the values ​​in the previous array. value.

For example:

$array1 = array('a' => 1, 'b' => 2, 'c' => 3);
$array2 = array('a' => 4, 'd' => 5);
$result = array_merge($array1, $array2);
print_r($result);

Above The code will output the following results:

Array
(

[a] => 4
[b] => 2
[c] => 3
[d] => 5

)

As you can see, since the key name in $array2 is duplicated with the key name in $array1 , so the value in $key => value in the result array is the value in $array2.

4. Merging multi-dimensional arrays

The array_merge() function can also merge multi-dimensional arrays, but it can only handle the merging of two arrays. If you need to merge multiple multi-dimensional arrays, you need to call the array_merge() function nestedly.

The following is an example of merging two multidimensional arrays:

$array1 = array('a' => array('b' => 1, 'c' => 2));
$array2 = array('a' => array('d' => 3));
$result = array_merge($array1, $array2);
print_r( $result);

The above code will output the following results:

Array
(

[a] => Array
    (
        [b] => 1
        [c] => 2
        [d] => 3
    )

)

As you can see, the The a array and the a array in $array2 are merged together and form a new associative array.

It should be noted that when merging multi-dimensional arrays, if the same key name appears, the value in the latter array will overwrite the value in the previous array. Therefore, when merging multi-dimensional arrays, the key name issue needs to be handled carefully.

Summary

In PHP programming, using the array_merge() function can more conveniently merge multiple arrays. Whether merging index arrays or associative arrays, the array_merge() function can easily complete the task. It should be noted that when there are the same key names, the values ​​in the latter array will overwrite the values ​​in the previous array. In addition, when you need to merge multi-dimensional arrays, you need to pay attention to the processing of key names.

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