php数组相加会合并重复值么

1. Introduction

PHP arrays are a versatile data structure that allows developers to store and manipulate multiple values in a single variable. One common operation performed on arrays is merging or adding them together. In this article, we will explore whether adding arrays in PHP merges duplicate values or not.

2. PHP Array Addition

PHP provides the array_merge() function to add arrays together. Let's consider an example where we have two arrays, $array1 and $array2, and we want to merge them.

$array1 = ["apple", "banana", "orange"];

$array2 = ["orange", "grape", "kiwi"];
$result = array_merge($array1, $array2);
print_r($result);

The expected output is:

Array

(
    [0] => apple
    [1] => banana
    [2] => orange
    [3] => orange
    [4] => grape
    [5] => kiwi
)

As we can see, the array_merge() function merges the two arrays by appending the elements of the second array to the first array. However, it does not remove any duplicate values. The resulting array contains all the elements from both input arrays, including the duplicate value "orange".

3. PHP Array Addition and Duplicate Values

3.1. Merging Arrays with Duplicate Values

Now let's explore what happens when we add arrays together and there are duplicate values present. Consider the following example:

$array1 = ["apple", "banana", "orange"];

$array2 = ["orange", "grape", "kiwi"];
$result = $array1 + $array2;
print_r($result);

The expected output is:

Array

(
    [0] => apple
    [1] => banana
    [2] => orange
)

When using the + operator to add arrays together, PHP preserves only the unique values from the first array and discards any duplicate values from the second array. In the example above, "orange" is present in both arrays, but only one occurrence is included in the resulting merged array.

3.2. Merging Arrays with Numeric Keys

When merging arrays with numeric keys, PHP behaves differently. Consider the following:

$array1 = [0 => "apple", 1 => "banana"];

$array2 = [1 => "orange", 2 => "grape"];
$result = $array1 + $array2;
print_r($result);

The expected output is:

Array

(
    [0] => apple
    [1] => banana
    [2] => grape
)

When the array keys are numeric and there are duplicate keys, the resulting merged array keeps the values from the first array and discards any duplicate values from the second array. In the example above, the value "orange" is discarded because the key 1 is already present in the first array.

4. Conclusion

In conclusion, when adding arrays together in PHP using the array_merge() function, duplicate values are not automatically removed. However, when using the + operator to merge arrays, duplicate values are discarded, and only unique values are preserved.

It is important to consider the behavior of array addition in PHP when working with arrays that may contain duplicate values. Temperature=0.6