How to implement array flipping in PHP (4 methods)

PHP is a very popular programming language, and it is often necessary to flip arrays during development. This article will introduce how to implement array flipping in PHP.

1. Using the array_reverse() function

The array_reverse() function is a built-in function in PHP that can flip the array. The syntax is as follows:

array array_reverse ( array $array [, bool $preserve_keys = FALSE ] )

Among them, $array indicates the array to be flipped, $preserve_keys indicates whether to retain the key names of the original array, and the default is FALSE.

The following is an example:

$arr = array(1, 2, 3, 4, 5);
$arr = array_reverse($arr);
print_r($arr);

The output result is as follows:

Array
(
    [0] => 5
    [1] => 4
    [2] => 3
    [3] => 2
    [4] => 1
)

2. Loop to exchange array element positions

In addition to using array_reverse( ) function, you can also complete the array flipping operation through a loop. The specific ideas are as follows:

(1) Define the variable $len to represent the array length;

(2) The number of loops is half of the array length, and each loop exchanges the elements at the corresponding positions;

(3) After completing the loop, the flip of the original array is achieved.

The following is a sample code:

$arr = array(1, 2, 3, 4, 5);
$len = count($arr);

for($i = 0; $i < $len / 2; $i++) {
    $temp = $arr[$i];
    $arr[$i] = $arr[$len - $i - 1];
    $arr[$len - $i - 1] = $temp;
}
print_r($arr);

The output result is as follows:

Array
(
    [0] => 5
    [1] => 4
    [2] => 3
    [3] => 2
    [4] => 1
)

3. Using the array_reduce() function

array_reduce() function It is a function built into PHP that can iterate over an array to achieve flipping operations. The specific ideas are as follows:

(1) Use the array_reduce() function to iterate the original array, and insert elements into the beginning of the result array in each iteration;

(2) After completing the iteration, The resulting array is the flip of the original array.

The following is a sample code:

$arr = array(1, 2, 3, 4, 5);

$arr = array_reduce($arr, function($result, $value) {
    array_unshift($result, $value);
    return $result;
}, array());

print_r($arr);

The output result is as follows:

Array
(
    [0] => 5
    [1] => 4
    [2] => 3
    [3] => 2
    [4] => 1
)

4. Using the array_flip() function

array_flip() function The keys and values ​​in the array can be exchanged to achieve flipping operations. The specific ideas are as follows:

(1) Use the array_flip() function to exchange the original array and obtain a new array with the key name being the value in the original array and the key value being the key name in the original array;

(2) After completing the exchange, sort the new array to obtain the new flipped array.

The following is the sample code:

$arr = array(1, 2, 3, 4, 5);

$arr = array_flip($arr);
ksort($arr);

print_r($arr);

The output result is as follows:

Array
(
    [1] => 5
    [2] => 4
    [3] => 3
    [4] => 2
    [5] => 1
)

To sum up, the flip operation of PHP array can be implemented in various ways. Depending on the actual situation and needs, choosing the most appropriate method can greatly improve development efficiency and code quality.

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