How to reverse php array

How to implement array reversal in php: 1. Use the "function reverse($arr){...}" method to achieve array reversal; 2. Use "function reverse_arr($arr){... }" method can be used to reverse the array.

#The operating environment of this article: Windows 7 system, PHP version 7.4, Dell G3 computer.

php implements array reversal

There is a function in php that can reverse an array, which is often used in work and is very convenient. Let’s implement this function by ourselves today.

$arr = [2,5,6,1,8,16,12];
function reverse($arr){
    $left = 0;
    $right = count($arr) -1;
    $temp = [];
    while ($left <= $right){
        $temp[$left] = $arr[$right];
        $temp[$right]  = $arr[$left];
        $left++;
        $right--;
    }
    ksort($temp);
    return $temp;
}

效果

Array
(
    [0] => 12
    [1] => 16
    [2] => 8
    [4] => 6
    [5] => 5
    [6] => 2
)

However, this function can only handle one-dimensional arrays. While implementing one that can handle multiple dimensions.

$arr = [2,[6,3,9],1,[5,2,1,[10,8,7]],5,0];

function reverse_arr($arr){
    $index = 0;
    $reverse_array = [];
    foreach ($arr as $sub_arr){
        if(is_array($sub_arr)){
            $sub_arr = reverse($sub_arr);
            $arr_ = reverse_arr($sub_arr);
            $reverse_array[$index] = $arr_;
        }else{
            $reverse_array[$index] = $sub_arr;
        }
        $index++;
    }
    return $reverse_array;
}

print_r(reverse(reverse_arr($arr)));

输出结果

Array
(
    [0] => 0
    [1] => 5
    [2] => Array
        (
            [0] => Array
                (
                    [0] => 7
                    [1] => 8
                    [2] => 10
                )

            [1] => 1
            [2] => 2
            [3] => 5
        )

    [3] => 1
    [4] => Array
        (
            [0] => 9
            [1] => 3
            [2] => 6
        )

    [5] => 2
)

The above are all numeric index arrays and cannot handle associative arrays. Next comes the one that can handle associative arrays

$arr = ['a'=>'aa','b'=>'bb','c'=>'cc','d'=>'dd','e'=>'ee'];
function reverse($arr){
    $temp = [];
    end($arr);
    while (($value = current($arr)) != null){
        $temp[key($arr)] = $value;
        prev($arr);
    }
    return $temp;
}
print_r(reverse($arr));

结果
Array
(
    [e] => ee
    [d] => dd
    [c] => cc
    [b] => bb
    [a] => aa
)

Recommended learning: "PHP Video Tutorial 》

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