Detailed explanation of how PHP uses functions to reverse arrays

PHP provides many array operation functions, which can often help us solve some common problems. This article will explain how to reverse array operations in PHP.

What is PHP array inversion?

In PHP, for a one-dimensional array, array reversal refers to reversing the order of each element in the array. For example, the original order of array elements is A, B, C. After reversing, the order of C, B, A is obtained.

In PHP, a built-in function array_reverse() is provided, which can be used to reverse the order of elements in an array.

The sample code is as follows:

$array = array("A", "B", "C");
$reversedArray = array_reverse($array);

After execution, the elements in $reversedArray will change to the order of C, B, and A.

If you want to retain the original key name of the array, you can use the second parameter setting of the array_reverse() function:

$array = array("A" => 1, "B" => 2, "C" => 3);
$reversedArray = array_reverse($array, true);

After the execution is completed, the The key name will remain unchanged, the order of elements is C, B, A, and the corresponding values ​​are 3, 2, and 1 respectively.

For two-dimensional arrays, if you need to reverse each sub-array, you can take the following method:

$array = array(
    array("A", "B", "C"),
    array("D", "E", "F"),
    array("G", "H", "I")
);
foreach ($array as &$subArray) {
    $subArray = array_reverse($subArray);
}
unset($subArray);

After execution, each sub-array in the $array array The order of the elements will be reversed.

Note that $subArray should be preceded and followed by & symbols, because in the foreach loop, the subarray is passed as a reference , if the & symbols are not added, the final result will be incorrect.

In actual development, array reversal is often a very common operation. PHP's built-in function array_reverse() can help us quickly achieve this goal and improve the efficiency of code writing.

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