How to merge arrays in PHP without changing the order

With the continuous development of the Internet, Web programs have become a tool used by more and more people. Among them, the PHP language is undoubtedly one of the most popular web backend languages. In PHP, arrays are a data type often used by developers, which can quickly store and manage large amounts of data. Among them, merging arrays is a very common operation. However, when we merge arrays, we often encounter the need to maintain the original order. This article will show you how to merge arrays in PHP without changing their order.

1. Merging arrays

In PHP, you can use the operator to merge arrays, such as the following example:

$a = array('apple', 'banana', 'orange');
$b = array('pear', 'grape', 'kiwi');
$c = $a + $b;
print_r($c);

Above The code will output the following content:

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

As you can see, when using the operator to merge arrays, if the key names of the two arrays are the same, the first array will prevail. Automatically rebuild numeric indexes.

2. Merge method that maintains the order of arrays

If we want to merge two arrays and want to maintain their original order, we can use array_merge( in PHP ) function. This function merges multiple arrays in the order they are passed and does not automatically rebuild numeric indices.

For example, the following code is an example of array merging using the array_merge() function:

$a = array('apple', 'banana', 'orange');
$b = array('pear', 'grape', 'kiwi');
$c = array_merge($a, $b);
print_r($c);

The above code will output the following:

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

As you can see from the output results, when using array_merge() to merge arrays, the original order can be maintained and the numeric index will not be automatically rebuilt.

In addition, if we want to retain the values ​​corresponding to the same key names while maintaining the order, we can use the array_replace() function. This function will overwrite the values ​​of the same key in the previous array with the values ​​in the later array, while maintaining the original order. For example, the following example:

$a = array('apple', 'banana', 'orange');
$b = array('banana', 'pear', 'grape');
$c = array_replace($a, $b);
print_r($c);

The output result is:

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

As you can see from the output result, after running the array_replace() function, the "banana" replaces "banana" in the first array while preserving the original order.

3. Summary of array merging

This article introduces the method of merging arrays in PHP and maintaining the original order. Among them, the operator can merge two arrays into one array, but will automatically rebuild the numeric index; and the array_merge() function can maintain the original order without automatically rebuilding the numeric index. Index; in addition, the array_replace() function can retain the values ​​corresponding to the same key names while maintaining the order.

No matter which method is used, we should choose the most suitable method according to the actual application scenario. I hope this article can provide you with a reference for merging arrays in PHP.

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