PHP array flashback changes key value

In PHP programming, array is a very commonly used data structure. Arrays can store multiple values ​​in programming, and each value can be accessed through key-value pairs. In some cases, we need to sort the key values ​​of an array in reverse order and keep the corresponding original values ​​unchanged. This requires the use of some specific functions and techniques in PHP.

Let me share with you some commonly used methods to sort PHP arrays in reverse order and change their key values.

Method 1: Use the array_reverse() function

The array_reverse() function in PHP can be used to reverse the order of the array. This function returns a new array with the same values ​​as the original array, with the keys renumbered.

$arr = array('A', 'B', 'C', 'D');
$reversedArr = array_reverse($arr);
print_r($reversedArr);

The output result is as follows:

Array
(
    [0] => D
    [1] => C
    [2] => B
    [3] => A
)

If you want to retain the original key value, you can set the second parameter to true.

$arr = array('A', 'B', 'C', 'D');
$reversedArr = array_reverse($arr, true);
print_r($reversedArr);

The output results are as follows:

Array
(
    [3] => D
    [2] => C
    [1] => B
    [0] => A
)

Method 2: Use the array_flip() function

The array_flip() function in PHP can interchange the keys and values ​​in the array. Returns a new array in which the original keys become values ​​and the original values ​​become keys. You can use this function to first exchange the keys and values ​​in the original array, and then use the array_reverse() function to reverse it.

$arr = array('A' => 1, 'B' => 2, 'C' => 3, 'D' => 4);
$flippedArr = array_flip($arr);
$reversedArr = array_reverse($flippedArr, true);
print_r($reversedArr);

The output results are as follows:

Array
(
    [4] => A
    [3] => B
    [2] => C
    [1] => D
)

Method 3: Use foreach loop

In PHP, you can use foreach loop to traverse the array and obtain each key-value pair. Then reassign it to a new array and use the decrement sign -- to create a reversed key value.

$arr = array('A' => 1, 'B' => 2, 'C' => 3, 'D' => 4);
$reversedArr = array();
$keys = array_keys($arr);
$num = count($keys);
for ($i = $num - 1; $i >= 0; $i--) {
    $key = $keys[$i];
    $reversedArr[$num - $i] = $arr[$key];
}
print_r($reversedArr);

The output results are as follows:

Array
(
    [1] => 4
    [2] => 3
    [3] => 2
    [4] => 1
)

The above are the detailed introduction of several commonly used methods to sort PHP arrays in reverse order and change their corresponding key values. You can choose to use different methods according to the actual situation.

The above is the detailed content of PHP array flashback changes key value. For more information, please follow other related articles on the PHP Chinese website!