The difference between PHP array merging and adding

With the development of the Internet, website development has gradually become an area that people pay attention to. In the process of website development, data processing is a very important part. As a programming language widely used in the fields of computer programming and website development, PHP language has its unique advantages and characteristics. In PHP, arrays are one of the commonly used data structures, and arrays can be merged and added. However, there are certain differences between these two operations in practical applications. This article will focus on the difference between array merging and addition in PHP, and provide relevant sample code.

1. PHP array merging operation

In PHP, array merging refers to merging elements in two or more arrays into one array. PHP provides two functions to implement array merging: array_merge() and array_merge_recursive().

1. array_merge()

array_merge() function merges multiple arrays. Its syntax format is: array array_merge ( array $array1 [, array $.. . ] ). When using the array_merge() function, you need to pass in the arrays to be merged, and the function will merge the elements of these arrays into a new array and return this new array. The order of the elements in the new array is consistent with the output order.

The following is an example of using the array_merge() function:

$array1 = array("fruit" => "apple", "drink" => "coffee");
$array2 = array("vegetable" => "carrot", "drink" => "tea");
$result = array_merge($array1, $array2);
print_r($result);

Output result:

Array
(
    [fruit] => apple
    [drink] => tea
    [vegetable] => carrot
)

It can be seen that both $array1 and $array2 have the "drink" key value, but the merged array only retains the latter value, which is the value corresponding to the "drink" key value in $array2.

2. array_merge_recursive()

array_merge_recursive() function also merges multiple arrays, but unlike array_merge(), it merges values ​​with the same key into an array instead of overwriting. Values ​​with the same key will be merged into an array. Its syntax format is: array array_merge_recursive ( array $array1 [, array $... ] ).

The following is an example of using the array_merge_recursive() function:

$array1 = array("fruit" => "apple", "drink" => "coffee", "color" => array("red", "green"));
$array2 = array("vegetable" => "carrot", "drink" => "tea", "color" => array("yellow"));
$result = array_merge_recursive($array1, $array2);
print_r($result);

Output result:

Array
(
    [fruit] => apple
    [drink] => Array
        (
            [0] => coffee
            [1] => tea
        )

    [color] => Array
        (
            [0] => red
            [1] => green
            [2] => yellow
        )

    [vegetable] => carrot
)

It can be seen that both $array1 and $array2 have the "color" key values, but the merged array merges them into a single array.

2. PHP array addition operation

In PHP, array addition refers to adding the corresponding elements in two arrays to form a new array. The addition operation is only allowed if the keys of the two arrays are integers or floating point numbers. When the key values ​​of two arrays are the same, their values ​​will be added accordingly. PHP provides an operator to implement array addition: (plus sign).

The following is an example of using operators:

$array1 = array(1, 2, 3);
$array2 = array(4, 5, 6);
$result = $array1 + $array2;
print_r($result);

Output result:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
)

It can be seen that since the key values ​​​​of the array are all integers, the addition operation only Merge the elements in $array1 and the elements with key values ​​4, 5, and 6 in $array2 into the new array, while the remaining elements are ignored.

When the key value of the array is not an integer or floating point number, the array addition operation is meaningless. For example:

$array1 = array("fruit" => "apple", "drink" => "coffee");
$array2 = array("vegetable" => "carrot", "drink" => "tea");
$result = $array1 + $array2;
print_r($result);

Output result:

Array
(
    [fruit] => apple
    [drink] => coffee
    [vegetable] => carrot
)

It can be seen that since the key value of the array is not an integer or floating point number, the addition operation has no practical meaning.

3. The difference between PHP array merging and addition

Array merging and addition both merge multiple arrays into one array, but their difference is:

1. The merge operation will overwrite or merge duplicate key values, while the addition operation only adds elements whose key values ​​are integers or floating point numbers.
2. Merge operations can be performed using the array_merge() function and array_merge_recursive() function, while addition operations can only be performed using the operator.
3. For the same key value, the merge operation may overwrite the original value, while the addition operation will only add the values ​​of the two arrays accordingly.

In short, in PHP, array merge and addition operations are common array operations, but they are different in application scenarios and operation methods. It is necessary to choose the appropriate operation method according to actual needs to achieve more efficient code writing.

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