How to merge arrays in php without removing duplicate data

The method for php to merge arrays without removing duplicate data is: by using the array_merge_recursive function, you can merge arrays without removing duplicate data, but merge the duplicate data into a sub-array, so that all data can be retained. And no duplicate data will be lost.

The operating environment of this tutorial: windows10 system, php8.1.3 version, DELL G3 computer.

In PHP, you can use the array_merge function to merge two arrays. The function of the array_merge function is to merge one or more arrays into a new array. However, the array_merge function will deduplicate duplicate data. If we want to merge arrays without removing duplicate data, we can use the array_merge_recursive function.

The array_merge_recursive function has similar functions to the array_merge function, but it does not remove duplicate data. When the same key name exists in the array, the array_merge_recursive function will merge the data with the same key name into a subarray.

Syntax:

array_merge_recursive ( array $array1 [, array $... ] ) : array

Parameter description:

-$array1：要合并的第一个数组，必需。
-$...：要合并的其他数组，可选。

Return value:

The merged array.

The following is an example to demonstrate the use of the array_merge_recursive function:

$array1=array('a'=>'apple','b'=>'banana');
$array2=array('a'=>'orange','c'=>'cherry');
$array3=array('d'=>'durian');
$result=array_merge_recursive($array1,$array2,$array3);
print_r($result);
输出结果：
Array
(
[a]=>Array
(
[0]=>apple
[1]=>orange
)
[b]=>banana
[c]=>cherry
[d]=>durian
)

As you can see, the key 'a' in array $array1 and array $array2 is repeated, but it is merged through the array_merge_recursive function Finally, the duplicate keys are merged into a subarray.

It should be noted that if the same key name has non-array and array when merging arrays, the array_merge_recursive function will convert the non-array value into an array.

For example:

$array1=array('a'=>'apple','b'=>'banana');
$array2=array('a'=>array('orange','cherry'));
$result=array_merge_recursive($array1,$array2);
print_r($result);
输出结果：
Array
(
[a]=>Array
(
[0]=>apple
[1]=>Array
(
[0]=>orange
[1]=>cherry
)
)
[b]=>banana
)

In the above example, the key 'a' in the array $array2 is an array, and the key 'a' in the array $array1 is a string. After merging through the array_merge_recursive function, the key 'a' in the array $array1 will be converted into an array.

To summarize, by using the array_merge_recursive function, we can not remove duplicate data when merging arrays, but merge the duplicate data into a sub-array. This way all data is retained and duplicate data is not lost .

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