How to keep the keys unchanged when merging php arrays

In PHP, array is a very common data structure that often needs to be operated and processed. Array merging is one of the common operations that combines two or more arrays into a larger array. Normally, when merging arrays, the key names are modified and the original key names are replaced with new key names, but sometimes it is necessary to merge arrays without changing the key names. So, how to merge arrays in PHP while keeping the key names unchanged? Next, we will introduce the methods and techniques to achieve this through this article.

1. Basics of PHP array merging

In PHP, you can use the array_merge() function and operator to merge arrays. The implementation methods and effects of these two methods are basically the same, but there are still some subtle differences:

1. array_merge() function

array_merge() function merges one or more Arrays are combined into one array. This function returns a new array containing all the elements in the parameter array. When merging, the key names will be rearranged according to the order of merging. That is, the following array will replace the same key name in the previous one. The specific syntax is as follows:

array array_merge ( array $array1 [, array $array2 [, array $... ]] )

The sample code is as follows:

$array1 = array("name"=>"张三", "age"=>20);
$array2 = array("age"=>25, "email"=>"zhangsan@gmail.com");
$array3 = array_merge($array1, $array2);
print_r($array3);

Running result:

Array (
    [name] => 张三
    [age] => 25
    [email] => zhangsan@gmail.com
)

2. Operator

Operator can Used for merging arrays, and can retain the original key names. When there are duplicate key names, the subsequent array will overwrite the previous array. The specific usage method is as follows:

$newsArray = array("title"=>"新闻标题", "content"=>"新闻内容");
$imageArray = array("title"=>"图片标题", "url"=>"http://www.example.com/image.jpg");
$finalArray = $newsArray + $imageArray;
print_r($finalArray);

Running results:

Array (
    [title] => 新闻标题
    [content] => 新闻内容
    [url] => http://www.example.com/image.jpg
)

2. PHP array merging keys remain unchanged

By default, when merging arrays in the above two ways, the key name All will change. But sometimes, we need to perform merge operations based on the original key names. At this time, you can use the array_replace() function, which can replace the value with the same key name in the previous array with the value of the later array, while retaining the original key name. If you need to merge multiple arrays, you can call them one after another.

1. array_replace() function

array_replace() function replaces the value with the same key name in the previous array with the value in the following array, while retaining the original key name . The specific usage method is as follows:

$array1 = array("name"=>"张三", "age"=>20);
$array2 = array("age"=>25, "email"=>"zhangsan@gmail.com");
$array3 = array_replace($array1, $array2);
print_r($array3);

Running result:

Array (
    [name] => 张三
    [age] => 25
    [email] => zhangsan@gmail.com
)

At this time, the original key names and order of array $array1 remain unchanged, and the contents of $array2 are overwritten into $array1. .

2. Merging multiple arrays

If you need to merge multiple arrays, you can call the array_replace() function in sequence, for example:

$array1 = array("name"=>"张三", "age"=>20);
$array2 = array("age"=>25, "email"=>"zhangsan@gmail.com");
$array3 = array("city"=>"北京", "gender"=>"男");
$finalArray = array_replace($array1, $array2, $array3);
print_r($finalArray);

Run result:

Array (
    [name] => 张三
    [age] => 25
    [email] => zhangsan@gmail.com
    [city] => 北京
    [gender] => 男
)

At this time, the key names and order in the array $finalArray are the same as those in $array1, while the key names and values ​​in the arrays $array2 and $array3 are overwritten to $ in finalArray.

3. Summary

Generally speaking, there are many ways to implement array merging in PHP, and you can choose different methods according to your needs. When it is necessary to perform a merge operation without changing the key name, the array_replace() function is a very convenient way to implement it. Using this function, you can merge the contents of one or more arrays into the first array while maintaining the order of the original key names. At the same time, you need to pay attention when using this function: there is no limit to the number of arrays to be merged, but if the key names in the arrays are the same, the values ​​in the subsequent arrays will overwrite the corresponding key values ​​in the previous arrays.

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