PHP method example of merging arrays and retaining key values

php merges arrays, generally using the array_merge method. array_merge — Merge one or more arrays

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

array_merge Merges the elements of one or more arrays, appending the values ​​in one array to the previous array and returning the resulting array.

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 subsequent 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, Key names with 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, the answers to the two parts of the multiple-choice questions in the questionnaire need to be merged together, and the answers to each part are It is an array (key=>value), 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) is a number, the key name will be re-indexed, resulting in the question The number cannot be reserved.

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
)

Use the "+" operator to merge arrays, you can retain the key values ​​of the array, if merged If the array contains the same key value, the later key value will not overwrite the previous key value (the previous key value takes precedence).

Related recommendations:

php merge array function array_merge()

The difference between php merging arrays using the + operator and the array function array_merge Detailed explanation of examples

Analysis of the difference between PHP merge array + and array_merge

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