How to convert key name and key value into each other in php

Conversion method: 1. Use the "array_flip($arr)" statement; 2. Use the "array_combine($arr,array_keys($arr))" statement; 3. Use "foreach($arr1 as $k =>$v){$arr2[$v]=$k;}" statement.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

php will change the key name and Key-value mutual conversion

#1. Use the array_flip() function

php to convert key names and key values ​​to each other. Simply put, it is to exchange arrays. The key name and key value in .

For this operation, there is a built-in function in PHP that has this function, that is the array_flip() function.

array_flip() function is used to exchange keys and values ​​​​in the array. Its syntax is as follows:

array_flip ($array)

$array The value in the array needs to be a legal key name, for example, it needs to be integer or string. A warning will be emitted if the value is of the wrong type, and the offending key-value pair will not be reversed.

If the same value appears multiple times, the last key name will be used as its value, and all others are lost.

Return value: The exchanged array is returned if the execution is successful, and NULL is returned if it fails.

Example:

<?php
$arr = array(&#39;a&#39;, &#39;b&#39;, &#39;1&#39;, 2, 3);
var_dump($arr);
var_dump(array_flip($arr));
?>

2. Use array_combine() and array_keys() functions

• array_keys() function can get the key names in the array and return the key name array

• array_combine() function by merging two arrays (one is the key name array and the other is the key name array) value array) to create a new array.

You only need to use the key array returned by the array_keys() function as the key value of the new array, and the original array as the key name of the new array.

<?php
$arr = array(&#39;a&#39;, &#39;b&#39;, &#39;1&#39;, 2, 3);
var_dump($arr);
var_dump(array_combine($arr,array_keys($arr)));
?>

3. Use foreach loop and an empty array

<?php
$arr1=array("aaa"=>11,"bbb"=>22,"ccc"=>33);
var_dump($arr1);
$arr2=array();
foreach($arr1 as $k=>$v){
	$arr2[$v]=$k;
}
var_dump($arr2);
?>

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