Introduction to the method of merging arrays and retaining key values ​​​​in PHP

php merges arrays, generally using the array_merge method.

array_merge — Merge one or more arrays

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

array_merge Merge the cells of one or more arrays, with the values ​​in one array appended to the front After an array, the resulting array is returned.

If the input array has the same string key name, the value after the key name will overwrite the previous value. However, if the array contains numeric keys, the latter will not overwrite the original value, but will be appended to it.

If only an array is given and the array is numerically indexed, the key names are re-indexed in a consecutive manner.


Example 1, the array uses string key names, the same key name will be overwritten by the following one

<?php$arr1 = array(&#39;name&#39;=>&#39;fdipzone&#39;);$arr2 = array(&#39;name&#39;=>&#39;terry&#39;);$result = array_merge($arr1, $arr2);

print_r($result);?>

Output:

Array(
    [name] => terry
)

Example 2, the array uses numeric key names, the same key names will not be overwritten, and the key names will be re-indexed

<?php
$arr1 = array(0=>&#39;fdipzone&#39;,1=>&#39;terry&#39;);
$arr2 = array(0=>&#39;php&#39;,1=>&#39;python&#39;);
$result = array_merge($arr1, $arr2);

print_r($result);?>

Output:

Array(
    [0] => fdipzone
    [1] => terry
    [2] => php
    [3] => python
)

Due to work needs, it is necessary to merge the answers to the two parts of the multiple-choice questions in the questionnaire. The answers to each part are arrays (key=>value), and the key is the question number. , value is the answer, and there is no duplication of question numbers in the two parts.

Use array_merge to merge the two parts of the answer

<?php
$form_data1 = array(11=>&#39;A&#39;,12=>&#39;B&#39;,13=>&#39;C&#39;,14=>&#39;D&#39;);
$form_data2 = array(25=>&#39;B&#39;,26=>&#39;A&#39;,27=>&#39;D&#39;,28=>&#39;C&#39;);
$result = array_merge($form_data1, $form_data2);

print_r($result);?>

Output:

Array(
    [0] => A
    [1] => B
    [2] => C
    [3] => D
    [4] => B
    [5] => A
    [6] => D
    [7] => C
)

Use array_merge to merge because the question number (key) It is a number, so the key name will be re-indexed, resulting in the question number not being retained.


Method to merge arrays and retain key values:

<?php
$form_data1 = array(11=>&#39;A&#39;,12=>&#39;B&#39;,13=>&#39;C&#39;,14=>&#39;D&#39;);
$form_data2 = array(25=>&#39;B&#39;,26=>&#39;A&#39;,27=>&#39;D&#39;,28=>&#39;C&#39;);
$result = $form_data1 + $form_data2;

print_r($result);?>

Output:

Array(
    [11] => A
    [12] => B
    [13] => C
    [14] => D
    [25] => B
    [26] => A
    [27] => D
    [28] => C
)

Using the "+" operator to merge arrays can retain the key values ​​​​of the array. If the merged array contains the same key value, the later one will not overwrite the previous key value (the previous one priority).

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